Trying to figure out on the off chance this ever comes up, if anyone has done it before and has suggestions on how to play it. I know that some subclasses would be harder to switch between. But I imagine that some of the caster classes might be easier to handle. IE I can imagine how and why a life domain cleric becomes a war domain cleric, I can’t figure out how and why an assassin becomes an arcane trickster.
I think I'm missing the purpose that you're trying to achieve in this question. Are you asking to make it to X-level as subclass-1, then from level-Y on, be subclass-2 in addition to subclass-1?
So, what did your DM say when you asked them the same question?
“Travel is fatal to prejudice, bigotry, and narrow-mindedness, and many of our people need it sorely on these accounts. Broad, wholesome, charitable views of men and things cannot be acquired by vegetating in one little corner of the earth all one's lifetime.” - Mark Twain - Innocents Abroad
"Retraining" a character is a common thing. One popular approach for Class --> Class retraining is to let players swap levels when they gain levels.(e.g. Fighter 5 --> Fighter 4 / Rogue 2 --> Fighter 3 / Rogue 4 --> etc...) This maintains a level of continuity throughout the campaign. However, subclasses aren't so easily transitioned.
In that case, I would just tie it into a downtime activity. Maybe the Wizard studies under a new arcane school for a while, or the Rogue gets a new mentor. Either way, if it makes the game more enjoyable, it's worth letting players adapt their characters. Sometimes that requires a bit of handwaving.
No I was thinking more along the lines of “get to level X as a Life cleric, then due to story reasons (let’s say a big war against an army of evil) the player becomes a champion for a god/goddess of battle and thus “temporarily” shifts to a war domain cleric with all those subclass specific buffs (but losing out on the life domain buff)
I had a rogue player who made his first character. He started off as an assassin.
Around level 3 he decided that because of his background he felt that Thief was more appropriate. He didn't feel like an assassin. So he just switched to Thief.
Then just as he was hitting level 5, he just wanted to become an Arcane Trickster. The party had just experienced a global mystical cataclysm, and he'd struck up a deal to act as a spy for a lich that the party had accidentally freed. It made sense that his connection to the lich might have imbued him with magic powers, so he slowly started discovering his newfound powers. This sounds pretty rapid, but it all took place over about nine months of fortnightly gameplay, and it was his first character so he was still learning.
As a general rule, player fun comes before anything else. If a player wants to change their character, change their subclass, or whatever else then it's best to just find a way to story it into your game. A cleric leaving one deity for another is a piece of cake. Changing from being a Necromancer to an Evoker is harder to explain, but since the DM can literally make up anything he wants and blame it on gods, it's far from beyond your powers.
"Temporarily" switching sub-classes sounds like more trouble than it's worth. In that kind of situation, I'd just give the player a custom Boon to grant them new abilities that can easily be added/removed.
There are rules for it in Tasha’s. Basically, if your DM says it’s ok, you can. And then they’ll make it as easy or difficult for you as they feel appropriate. Like if you experienced some kind of strange thing in the story, like in sanvael’s example, they may just let you. But if you don’t have a good story reason, they may require some down time training or something.
I'm more prone to having a player roll up a whole new character than to have them swap back and forth between the abilities and class features that would suit them "temporarily". Also, Memnosyne landed on a great idea, could be an Artifact or Item that grants some benefit. It could easily be removed by said deity after a set time.
I'll stick with the stance of: I'm still unclear as to why you would go into character progression (generation?) with this question in mind. Are you hesitant to pick because of drastic story changes later in the campaign?
“Travel is fatal to prejudice, bigotry, and narrow-mindedness, and many of our people need it sorely on these accounts. Broad, wholesome, charitable views of men and things cannot be acquired by vegetating in one little corner of the earth all one's lifetime.” - Mark Twain - Innocents Abroad
Sometimes you can be really enjoying roleplaying a character, but find that the class choice you've made isn't the fun you thought it would be. This is a common problem for Barbarians, and in particular, the Wild Magic Barbarian.
You roll a Barbarian because you want to be an up-front, in your face fighter and hit stuff. You choose Wild Magic because it's a bit of fun. Unfortunately, by the time you're about level 6-7 you're looking at the way all encounters go for you, and the way that your future advancements go and... there's no difference at all for the next 13-14 levels. Moreover, you've had enough Wild Magic rolls that you've seen every effect multiple times (there are only 8), some of them don't do anything, and they don't scale so your main feature has actually become more like a chore at the start of combat.
So what do you do? The best answer is to multiclass, to open up more options. The player in my game took a level in Wild Magic Sorcerer to open up a bunch of cantrips and some out of combatty spells. But what if you don't have the Charisma? Probably don't have the Wis or Int to multiclass in those directions either. So either changing barbarian subclass (You finally go the wild magic out of your system!) or switching into a different class altogether ("I have finally calmed down, and learned the value of armor") might shake things up. There's no harm in doing this.
I would be open to a player changing sub-class once if they really don't like playing it but suddenly "forgetting" a whole collection of their abilities doesn't really fit in with character development.
Going to the OP's rogue. In the current situation, striking a deal with a lich strikes me very much like he has started the path of an undying warlock, I don't know if he has the charisma for it but if he does as he is about to hits 5th level he could take a level of warlock to get some magic from it. (if he doesn't have 13 cha you might be able ot work around it). Another multiclass option is the god of this lich could also grant the rogue divine magic (death cleric).
Feats are another way to get a bit of ,magic, shadow touched seems particulater appropriate but magic initiate (or any other feat giving access to spells) could be re-flavoured
RAW, you can switch a subclass at the level you would gain a subclass feature. You swap all of your other subclass features for the new one. What it takes to do this is left to the DM. It can be gradual- devoting time, spending money for training (suggests 100GP*level), and/or completing a quest. Or it can be sudden, with a story line character change. (Like the example in Tasha's- a devotion paladin failed, her home was wrecked, and she switched to vengeance on the destroyers after only one night of praying.)
My first Warlock started out as a Tomelock. Never having played one before, I wanted him to be more “intellectual” and unknowingly set him up with everything that was guaranteed to get his butt kicked.. No EB, no offensive Invocations, primarily utility spells, you get the picture. By the time we made it to 5 level, he was pretty much the party joke, to the extent that he claimed his patron was so disappointed that he had to change his name to Peggy Sue. He was no fun to play at all.
As a result, my DM and I talked it over and agreed that (instead of just killing him off and starting over new) i could change to a Chainlock and pick all new spells and Invocations. It was RP’d to the other players/characters by saying that his first patron was so upset with him that he was sold to a Fiend for 50 Gp and a case of beer.
In a case like this, switching was the right solution. I learned a valuable lesson, the party had some fun, and a cool story was told.
It's possible. It just needs to be handled properly. And there should be a process involved, either a period of retraining, or a climactic event that transforms the character. It happened recently in the group I play with.
Okay, so, one of the characters in my regular group was a half elf Inquisitive Rogue. The subclass had sounded interesting to the player, but after a half dozen levels of it she was starting to feel that something was just... lacking. Bear in mind, the character was a super-creepy gothy person to begin with. When Tasha's came out, the player fell in love with the idea of the Phantom Rogue. So, at the time, the group was going through a mansion in a creepy demiplane trying to clean out the vampires residing there. Near the end of that arc several of us suffered certain... injuries. My cleric had his Intelligence score drop from 9 down to 5. The bard was stricken with such fear that he soon after gave up adventuring and settled down got married and started making babies. And the rogue, well, there was no noticeable change to her. I mean, she was already kinda creepy. And yes, we the players noticed that some of her game mechanics had changed a bit, but our characters didn't know that. She was creepy and stabby before, and she's still creepy and stabby. We have just recently begun to realize that she has also been secretly feeding on a couple of characters in our sleep. Feeding... like with fangs... in the neck... Apparently she has not only switched from Inquisitive Rogue to Phantom Rogue, but has also transformed from a half elf to a dhamphir. She still looks the same... except for the fangs when she's feeding. And she still acts the same. So we surmised that when we were in that vampire mansion she must have gotten somehow infected by the vampires and is slowly turning into one. So of course my cleric is working on a way to save her from that fate.
Regarding the subclasses, we need to remember that our characters don't know all the things we know. We know the game mechanics. They only see a teammate stabbing things and maybe casting spells. As long as the player has a rational explanation to justify the change, and as long as the DM is able and willing to work the necessary changes into the storyline in a sensible way, then go for it.
If I were to allow it, unless there's a reason they would forget the ability, I would say that the in universe fiction is that the character never forgot those abilities, they just stopped using them. At the table, they no longer have access to those abilities, with the possible exception of adding narrative flair to things they can manage to do without the ability.
I have a player who is a Monk and wants to explore the various subclasses associated. I've been chewing on this idea for a while and I can understand his reasoning as he wants to learn about various "Ways Of..." as a person would want to study various religions and beliefs. My main goal was not to open up the character flipping subclasses at a drop of the hat.
The extend I've been thinking is the character needs to spend three uninterrupted months of non-adventure time in a monastery learning the new "Way Of..." subclass and then the old abilities of the previous subclass go away. The only catch is how to deal with the abilities granted since the character is starting this new subclass at a level other than 1st. I don't want to immediately give them the abilities but a way to slowly add them to the players' abilities as they demonstrate their new "Way of..." Again, nothing has been implemented, but I have thought about how I would run it if I ever pulled the trigger on such a Subclass change.
Now in another situation, I had where a Life Cleric had to change Subclass based on his action in one game. In short, the Life Cleric participated in severe torture of a bandit captain to get some information. I'm talking, the Life Cleric came close to waterboarding the poor guy and cutting a finger off. After that game I pretty much had the Life Cleric god take away the player abilities, spells, etc. When I talked to the player about what happened and the repercussions he totally understood and admitted he did the wrong thing and accepted the consequences with good grace. So I build a storyline where the once-cleric worked at finding a new god to accept him and grant its abilities to the player. So the players found a War god to become to represent as a cleric a few sessions later on after doing some serious soul-searching RP. So this subclass change was derived via the story narrative and not just I'm bored with this subclass.
As a side note, this character did not last long as it got beat up pretty bad in an encounter enough that a sort of PTSD was established and the player wanted to change characters as he felt this cleric sort of got away from his original idea on what he wanted. I understood and I granted him the change as I like the development of the cleric I used it as an NPC later on.
Its never come up before, to be honest. That said, as long as there's an in game reason for it (paladin oaths, changing your warlock patron, finding a different religion as a cleric, thief swearing off stealing and going swashbuckler, etc), I'd totally allow it.
Fundamentally, I feel that you shouldn't be asking "how do I change from Champion Fighter to Psi Knight," but rather, "hey, your character just got experimented on by mind flayers. Do you want some psychic powers?" Let the course of the story shape how things happen.
Tashas Cauldron includes rules allowing for changes of Sub class, it is something I have allowed before that was released, sometimes players stop enjoying the sub class they are playing and so I will allow them to swap it out. But from a storyline aspect I have had clerics swap the god they devoted themselves to, warlocks change patron, Wizards swap to a different school. A wild magic sorceror learnt to control her abilities and so changed.
Depends on the group I gamed with. Some I gave an ingame reasons, others as long as the rebuild between sessions I don't care. But IF you keep rebuilding/bring in new pc, I will NOT plant any cool items for your pc.
In games I've run I had a Paladin Rogue change Oaths when he took service with a dragon, from Oath of Glory to Oath of Dragonlords (Platinum Knight) which was homebrew. That same Paladin switched to be a Warlock when we had a 2 year gap between adventures. His story was that he was serving his dragon lord by carrying an evil magic sword as it's warden. He became a Warlock because of the swords outward effect on him and his nod to the previous class was a gold pseudodragon familiar. We had ruled that Paladins and Warlocks gained power from similar sources on a metaphysical level.
I also had a Feypact Warlock trade their levels for equal levels in Eloquence Bard as payment for their pact being complete.
I've had a rogue go assassin from treasure hunter after their pet badger was slain ala john wick.
I've had a sorcerer go from wild magic to draconic bloodline as part of discovering her mom was a dragon.
In your examples:
Assassin was forced to kill once upon a time but always wanted to be a member of the circus instead so they chase their dream. Or they discovered a previously hidden connection to magic that was awakened during a near death experience and it caused them to reevaluate the cost of a life. Maybe its not that they don't know how to kill, but they are choosing not too unless in self defense or they generally avoid killing where possible.
Clerics changing are easier because its based on the Gods who are recognized as real by everyone (in forgotten realms anyways). So they could have been converted to a new religion, corrupted or sought out by a god who was stealing or brainwashing followers from another god. The God might be a pretender who after stealing the domain of a lesser deity they are using it to break their followers. A War Domain Cleric could be spawned from a Life Cleric who is pushed (seemingly by their god) to kill so regularly that they loose faith in their ability as a healer. The god then reveals themselves to be one of War who know that the best warriors need to be without mercy (evil) or whose followers needed to learn the true value of a life before being asked to fight for the god or one of their war domain allies in some greater conflict.
Tho, in all cases I would avoid giving them everything right away. Either include time for training montages, a roleplay scene, or downtime where they practice before making the change. Alternately, you could have where they don't get all the new abilities all at once and instead you tell them when they can start using each one, or better yet, they roll for it during combat whenever they are under stress or complete a challenge that would normally award XP.
I think it would depend in part on the reason for the switch of subclass. Is the player just not having fun with the subclass they initially chose? If so, I would let my player just handwave a subclass switch, no in-game roleplay needed. Though if they want, the change can be worked into the story if possible. One of my players was an Artillerist Artificer but wanted to switch to Armorer, so we worked out an in-story event that enabled him to make the switch.
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Trying to figure out on the off chance this ever comes up, if anyone has done it before and has suggestions on how to play it. I know that some subclasses would be harder to switch between. But I imagine that some of the caster classes might be easier to handle. IE I can imagine how and why a life domain cleric becomes a war domain cleric, I can’t figure out how and why an assassin becomes an arcane trickster.
I think I'm missing the purpose that you're trying to achieve in this question. Are you asking to make it to X-level as subclass-1, then from level-Y on, be subclass-2 in addition to subclass-1?
So, what did your DM say when you asked them the same question?
“Travel is fatal to prejudice, bigotry, and narrow-mindedness, and many of our people need it sorely on these accounts. Broad, wholesome, charitable views of men and things cannot be acquired by vegetating in one little corner of the earth all one's lifetime.” - Mark Twain - Innocents Abroad
"Retraining" a character is a common thing. One popular approach for Class --> Class retraining is to let players swap levels when they gain levels.(e.g. Fighter 5 --> Fighter 4 / Rogue 2 --> Fighter 3 / Rogue 4 --> etc...) This maintains a level of continuity throughout the campaign. However, subclasses aren't so easily transitioned.
In that case, I would just tie it into a downtime activity. Maybe the Wizard studies under a new arcane school for a while, or the Rogue gets a new mentor. Either way, if it makes the game more enjoyable, it's worth letting players adapt their characters. Sometimes that requires a bit of handwaving.
No I was thinking more along the lines of “get to level X as a Life cleric, then due to story reasons (let’s say a big war against an army of evil) the player becomes a champion for a god/goddess of battle and thus “temporarily” shifts to a war domain cleric with all those subclass specific buffs (but losing out on the life domain buff)
I had a rogue player who made his first character. He started off as an assassin.
Around level 3 he decided that because of his background he felt that Thief was more appropriate. He didn't feel like an assassin. So he just switched to Thief.
Then just as he was hitting level 5, he just wanted to become an Arcane Trickster. The party had just experienced a global mystical cataclysm, and he'd struck up a deal to act as a spy for a lich that the party had accidentally freed. It made sense that his connection to the lich might have imbued him with magic powers, so he slowly started discovering his newfound powers. This sounds pretty rapid, but it all took place over about nine months of fortnightly gameplay, and it was his first character so he was still learning.
As a general rule, player fun comes before anything else. If a player wants to change their character, change their subclass, or whatever else then it's best to just find a way to story it into your game. A cleric leaving one deity for another is a piece of cake. Changing from being a Necromancer to an Evoker is harder to explain, but since the DM can literally make up anything he wants and blame it on gods, it's far from beyond your powers.
"Temporarily" switching sub-classes sounds like more trouble than it's worth. In that kind of situation, I'd just give the player a custom Boon to grant them new abilities that can easily be added/removed.
There are rules for it in Tasha’s. Basically, if your DM says it’s ok, you can. And then they’ll make it as easy or difficult for you as they feel appropriate. Like if you experienced some kind of strange thing in the story, like in sanvael’s example, they may just let you. But if you don’t have a good story reason, they may require some down time training or something.
I'm more prone to having a player roll up a whole new character than to have them swap back and forth between the abilities and class features that would suit them "temporarily". Also, Memnosyne landed on a great idea, could be an Artifact or Item that grants some benefit. It could easily be removed by said deity after a set time.
I'll stick with the stance of: I'm still unclear as to why you would go into character progression (generation?) with this question in mind. Are you hesitant to pick because of drastic story changes later in the campaign?
“Travel is fatal to prejudice, bigotry, and narrow-mindedness, and many of our people need it sorely on these accounts. Broad, wholesome, charitable views of men and things cannot be acquired by vegetating in one little corner of the earth all one's lifetime.” - Mark Twain - Innocents Abroad
Sometimes you can be really enjoying roleplaying a character, but find that the class choice you've made isn't the fun you thought it would be. This is a common problem for Barbarians, and in particular, the Wild Magic Barbarian.
You roll a Barbarian because you want to be an up-front, in your face fighter and hit stuff. You choose Wild Magic because it's a bit of fun. Unfortunately, by the time you're about level 6-7 you're looking at the way all encounters go for you, and the way that your future advancements go and... there's no difference at all for the next 13-14 levels. Moreover, you've had enough Wild Magic rolls that you've seen every effect multiple times (there are only 8), some of them don't do anything, and they don't scale so your main feature has actually become more like a chore at the start of combat.
So what do you do? The best answer is to multiclass, to open up more options. The player in my game took a level in Wild Magic Sorcerer to open up a bunch of cantrips and some out of combatty spells. But what if you don't have the Charisma? Probably don't have the Wis or Int to multiclass in those directions either. So either changing barbarian subclass (You finally go the wild magic out of your system!) or switching into a different class altogether ("I have finally calmed down, and learned the value of armor") might shake things up. There's no harm in doing this.
I would be open to a player changing sub-class once if they really don't like playing it but suddenly "forgetting" a whole collection of their abilities doesn't really fit in with character development.
Going to the OP's rogue. In the current situation, striking a deal with a lich strikes me very much like he has started the path of an undying warlock, I don't know if he has the charisma for it but if he does as he is about to hits 5th level he could take a level of warlock to get some magic from it. (if he doesn't have 13 cha you might be able ot work around it). Another multiclass option is the god of this lich could also grant the rogue divine magic (death cleric).
Feats are another way to get a bit of ,magic, shadow touched seems particulater appropriate but magic initiate (or any other feat giving access to spells) could be re-flavoured
RAW, you can switch a subclass at the level you would gain a subclass feature. You swap all of your other subclass features for the new one. What it takes to do this is left to the DM. It can be gradual- devoting time, spending money for training (suggests 100GP*level), and/or completing a quest. Or it can be sudden, with a story line character change. (Like the example in Tasha's- a devotion paladin failed, her home was wrecked, and she switched to vengeance on the destroyers after only one night of praying.)
Only spilt the party if you see something shiny.
Ariendela Sneakerson, Half-elf Rogue (8); Harmony Wolfsbane, Tiefling Bard (10); Agnomally, Gnomish Sorcerer (3); Breeze, Tabaxi Monk (8); Grace, Dragonborn Barbarian (7); DM, Homebrew- The Sequestered Lands/Underwater Explorers; Candlekeep
My first Warlock started out as a Tomelock. Never having played one before, I wanted him to be more “intellectual” and unknowingly set him up with everything that was guaranteed to get his butt kicked.. No EB, no offensive Invocations, primarily utility spells, you get the picture. By the time we made it to 5 level, he was pretty much the party joke, to the extent that he claimed his patron was so disappointed that he had to change his name to Peggy Sue. He was no fun to play at all.
As a result, my DM and I talked it over and agreed that (instead of just killing him off and starting over new) i could change to a Chainlock and pick all new spells and Invocations. It was RP’d to the other players/characters by saying that his first patron was so upset with him that he was sold to a Fiend for 50 Gp and a case of beer.
In a case like this, switching was the right solution. I learned a valuable lesson, the party had some fun, and a cool story was told.
It's possible. It just needs to be handled properly. And there should be a process involved, either a period of retraining, or a climactic event that transforms the character. It happened recently in the group I play with.
Okay, so, one of the characters in my regular group was a half elf Inquisitive Rogue. The subclass had sounded interesting to the player, but after a half dozen levels of it she was starting to feel that something was just... lacking. Bear in mind, the character was a super-creepy gothy person to begin with. When Tasha's came out, the player fell in love with the idea of the Phantom Rogue. So, at the time, the group was going through a mansion in a creepy demiplane trying to clean out the vampires residing there. Near the end of that arc several of us suffered certain... injuries. My cleric had his Intelligence score drop from 9 down to 5. The bard was stricken with such fear that he soon after gave up adventuring and settled down got married and started making babies. And the rogue, well, there was no noticeable change to her. I mean, she was already kinda creepy. And yes, we the players noticed that some of her game mechanics had changed a bit, but our characters didn't know that. She was creepy and stabby before, and she's still creepy and stabby. We have just recently begun to realize that she has also been secretly feeding on a couple of characters in our sleep. Feeding... like with fangs... in the neck... Apparently she has not only switched from Inquisitive Rogue to Phantom Rogue, but has also transformed from a half elf to a dhamphir. She still looks the same... except for the fangs when she's feeding. And she still acts the same. So we surmised that when we were in that vampire mansion she must have gotten somehow infected by the vampires and is slowly turning into one. So of course my cleric is working on a way to save her from that fate.
Regarding the subclasses, we need to remember that our characters don't know all the things we know. We know the game mechanics. They only see a teammate stabbing things and maybe casting spells. As long as the player has a rational explanation to justify the change, and as long as the DM is able and willing to work the necessary changes into the storyline in a sensible way, then go for it.
It's a game. Play! Have fun!
Anzio Faro. Protector Aasimar light cleric. Lvl 18.
Viktor Gavriil. White dragonborn grave cleric. Lvl 20.
Ikram Sahir ibn-Malik al-Sayyid Ra'ad. Brass dragonborn draconic sorcerer Lvl 9. Fire elemental devil.
Wrangler of cats.
If I were to allow it, unless there's a reason they would forget the ability, I would say that the in universe fiction is that the character never forgot those abilities, they just stopped using them. At the table, they no longer have access to those abilities, with the possible exception of adding narrative flair to things they can manage to do without the ability.
I have a player who is a Monk and wants to explore the various subclasses associated. I've been chewing on this idea for a while and I can understand his reasoning as he wants to learn about various "Ways Of..." as a person would want to study various religions and beliefs. My main goal was not to open up the character flipping subclasses at a drop of the hat.
The extend I've been thinking is the character needs to spend three uninterrupted months of non-adventure time in a monastery learning the new "Way Of..." subclass and then the old abilities of the previous subclass go away. The only catch is how to deal with the abilities granted since the character is starting this new subclass at a level other than 1st. I don't want to immediately give them the abilities but a way to slowly add them to the players' abilities as they demonstrate their new "Way of..." Again, nothing has been implemented, but I have thought about how I would run it if I ever pulled the trigger on such a Subclass change.
Now in another situation, I had where a Life Cleric had to change Subclass based on his action in one game. In short, the Life Cleric participated in severe torture of a bandit captain to get some information. I'm talking, the Life Cleric came close to waterboarding the poor guy and cutting a finger off. After that game I pretty much had the Life Cleric god take away the player abilities, spells, etc. When I talked to the player about what happened and the repercussions he totally understood and admitted he did the wrong thing and accepted the consequences with good grace. So I build a storyline where the once-cleric worked at finding a new god to accept him and grant its abilities to the player. So the players found a War god to become to represent as a cleric a few sessions later on after doing some serious soul-searching RP. So this subclass change was derived via the story narrative and not just I'm bored with this subclass.
As a side note, this character did not last long as it got beat up pretty bad in an encounter enough that a sort of PTSD was established and the player wanted to change characters as he felt this cleric sort of got away from his original idea on what he wanted. I understood and I granted him the change as I like the development of the cleric I used it as an NPC later on.
Its never come up before, to be honest. That said, as long as there's an in game reason for it (paladin oaths, changing your warlock patron, finding a different religion as a cleric, thief swearing off stealing and going swashbuckler, etc), I'd totally allow it.
Fundamentally, I feel that you shouldn't be asking "how do I change from Champion Fighter to Psi Knight," but rather, "hey, your character just got experimented on by mind flayers. Do you want some psychic powers?" Let the course of the story shape how things happen.
Tashas Cauldron includes rules allowing for changes of Sub class, it is something I have allowed before that was released, sometimes players stop enjoying the sub class they are playing and so I will allow them to swap it out. But from a storyline aspect I have had clerics swap the god they devoted themselves to, warlocks change patron, Wizards swap to a different school. A wild magic sorceror learnt to control her abilities and so changed.
Depends on the group I gamed with. Some I gave an ingame reasons, others as long as the rebuild between sessions I don't care. But IF you keep rebuilding/bring in new pc, I will NOT plant any cool items for your pc.
No Gaming is Better than Bad Gaming.
In games I've run I had a Paladin Rogue change Oaths when he took service with a dragon, from Oath of Glory to Oath of Dragonlords (Platinum Knight) which was homebrew. That same Paladin switched to be a Warlock when we had a 2 year gap between adventures. His story was that he was serving his dragon lord by carrying an evil magic sword as it's warden. He became a Warlock because of the swords outward effect on him and his nod to the previous class was a gold pseudodragon familiar. We had ruled that Paladins and Warlocks gained power from similar sources on a metaphysical level.
I also had a Feypact Warlock trade their levels for equal levels in Eloquence Bard as payment for their pact being complete.
I've had a rogue go assassin from treasure hunter after their pet badger was slain ala john wick.
I've had a sorcerer go from wild magic to draconic bloodline as part of discovering her mom was a dragon.
In your examples:
Assassin was forced to kill once upon a time but always wanted to be a member of the circus instead so they chase their dream. Or they discovered a previously hidden connection to magic that was awakened during a near death experience and it caused them to reevaluate the cost of a life. Maybe its not that they don't know how to kill, but they are choosing not too unless in self defense or they generally avoid killing where possible.
Clerics changing are easier because its based on the Gods who are recognized as real by everyone (in forgotten realms anyways). So they could have been converted to a new religion, corrupted or sought out by a god who was stealing or brainwashing followers from another god. The God might be a pretender who after stealing the domain of a lesser deity they are using it to break their followers. A War Domain Cleric could be spawned from a Life Cleric who is pushed (seemingly by their god) to kill so regularly that they loose faith in their ability as a healer. The god then reveals themselves to be one of War who know that the best warriors need to be without mercy (evil) or whose followers needed to learn the true value of a life before being asked to fight for the god or one of their war domain allies in some greater conflict.
Tho, in all cases I would avoid giving them everything right away. Either include time for training montages, a roleplay scene, or downtime where they practice before making the change. Alternately, you could have where they don't get all the new abilities all at once and instead you tell them when they can start using each one, or better yet, they roll for it during combat whenever they are under stress or complete a challenge that would normally award XP.
I think it would depend in part on the reason for the switch of subclass. Is the player just not having fun with the subclass they initially chose? If so, I would let my player just handwave a subclass switch, no in-game roleplay needed. Though if they want, the change can be worked into the story if possible. One of my players was an Artillerist Artificer but wanted to switch to Armorer, so we worked out an in-story event that enabled him to make the switch.