With the limitations and consequences way higher than they need to be other than the wish backfires, what is even the reason for including this as a castable spell? It's dulled down to the level of lesser wish of earlier editions. Just call it Lesser Wish and firm up the limits and take out the consequences and make the Wish a god tier thing that is granted for doing world-changing shit once in a while and stop being a dick about it. 

What level is the duplicated spell going to behave like? If I duplicate magic missile in this way, is it first level because that's lowest; eighth level because that's as high as wish can go; or ninth level because that's the slot being consumed? Likewise, what would the level of the spell be for the purpose of counterspell and dispel magic? I'd imagine the DC for counterspell would be 19, but what about dispel magic, which only takes effect after the casting?

Quote from isitaspider >>

Quote from Giffard >>

 if you lose the spell, and you are a caster that only have a certain number of spells like a bard or a sorcerer, are you able to choose a new spell to replace wish?

 

No. You aren't "losing" wish. You're losing the ability to cast wish. That's part of the inherent risk of the spell. If you use wish to wish for something outside of the bulleted items, you may lose your level 9 spell forever (barring some shenanigans like wishing to undo the loss of wish, which is just asking for DMs to screw with you). You don't get to replace it because you never lost it. It's more akin to losing a critical component to cast the spell than losing the spell itself.

Or, you know, you could just replace Wish with another spell when you gain a level.

Quote from the PHB:

Additionally, when you gain a level in this class, you can choose one of the sorcerer spells you know and replace it with another spell from the sorcerer spell list, which also must be of a level for which you have spell slots.

The use of the word 'additionally' implies that this can be done simultaneously to learning a new spell, but even if it didn't, by the time you can cast Wish, you will never learn any new spells from leveling anyway, so there's no downside to swapping out Wish for another spell.

why can't warlock do it D:<

Lets see if I can create a wish that cannot possibly be messed up by the DM.

"I wish to permanently double my hit point maximum, without any other side affects occurring, without affecting my position, without moving anybody or any object of any sort to any other position or plane, and without any other magical effects taking place."

Could someone find a way to mess this up? 

This spell stands out quite a bit from the others, and kinda represents magic as a whole, in that it can break all rules. On one hand, you can do (or at least try to do) ANYTHING you want (though it may fail). You could dispel magic that is specifically immune to dispelling, cause an army to drop dead, or perform feats that shouldn't be possible. On the other hand, doing so would severely weaken you to the point of being nearly useless, and you risk losing the ability to cast wish altogether. Not to mention, unless your DM is really nice, the effects will probably backfire. I would treat this spell as the ability to cast EVERY other spell of 8th level or lower without material components, and when you're really out of options, a last resort for just about anything.

If my genasi wizard character ever got their hands on a Ring of Three Wishes, they would totally have a Scarlett Witch moment ('no more mutants') and send out a cosmic wave of elemental energy, wishing say 1 in 4 children born in the next 100 years be a kind of genasi. Pretty much D&D X-men.

As a DM, how would you counteract this wish? What would be the balancing consequence or hidden affect?

i wish for my dad to come back

As to clone casting, I see no impediment in wish casting 8th level Clone "effective 119 days past at this very spot." It (probably) should not trigger stress. Risk instead is whether the locale is/was secure for that time period... or would have in light of a clone growing, and that is the potential rub.

"I wish no one could ever cast Wish henceforth!"

or..  during big bad's monologuing... "I wish you never wanted to do any of the evil things you did" ... poof, campaign is undone the party was never assembled, and characters never gained any levels.

"I wish your brain signals were suddenly reversed" tries to punch with one hand ends up pulling with the other... tries to cast a harmful spell, heals party instead

let them cast meteor swarm but it always targets the party.

as a DM I'd allow it, with these caveat's
you can permanently fly but you can never land...
you grow gills and can only breathe in water
you constantly fall so slowly, you're pretty much "grappled" by the air while falling for 2 turns.
you can keep up your spell without concentrating, but it uses a spell slot each turn, you can never dispell it so long as you have spell points, and you compulsively cast it every time you gain spell slots.
Your party gains resistance to that damage type, but are weak to all other types of damage.

Quote from SBMWaugh >>

Two steps to becoming an over powered PC:

1.  "I wish that every time that I cast the Wish spell, that a random evil creature experiences the strain in my stead."

2.  "I wish that I could cast Wish as often as I want, without cost" (The wording on this one can be altered if characters are supposed to know what spell slots are)

 

You then have unlimited wishes, as often as you want to make them.

 
1. As a DM, I'd also link all of any enemy's suffering to yours, permanently

2. Granted but your character only wishes for fish. (or other meaningless object)

Quote from TinCan_Whiplash >>

Quote from bearslord >>

Quote from Goddess_of_Chaos >>

Quote from Myraddin >>

I wish to be a dragon, with all my wizard skills.

 That’s basically casting Shapechange. 

 But it's permanent, unlike Shapechange

 This would absolutely be my Wish for most any character.

 "ok you become a small bearded dragon, and if you could speak you could cast spells.. but small lizards like that don't speak."

we ALL know that most DMs and players are gonna look at this and go"**** that, instead, your gonna become a deity" cause honestly this shit is kinda weak for basically the ultimate "haha **** you I'm the dm now haha"  

This spell has the greatest cause for consequence. The DM has so much power over the wish, and it could go horribly wrong. I love it.

Rule of thumb for me is that a wish can not include the word "and" because that would be wishing for multiple things in one wish, but there are some exceptions ex. i wish for a dress thats white and blue would be fine.

That aside for your wish there are plenty of ways to ruin it.

You specified Position and Plane not Realm or dimension, so all positions could remain but the but the realm could change Ex. A realm that exists in a gelatinous vitality potion, you are forever stuck within the potion that doubles your hit-points maximum, but are unable to escape.

You said anybody or any object, but anybody implies sapient creatures so anything creatures that are not wise enough to be sentient. Ex. A modified Suit of Animated armor, (a construct not an object) or even a Modified flesh golem engulfs your body Its magical ability increasing your maximum hit-points by combining your with theirs but due to their overwhelming power you can not resist their movement, in any way so you become part of them. 

Those are two ways that cause you to get your wish, follow the rules you set, end with you being trapped and also likely to suffocate (with the exception of the animated armor) and kill you very quickly. Of course that would be cruel so i would use the animated armor route that would mean you need to be trapped for 24 hours to make another wish, to reverse the wish because due to your qualifier of "permanently" the armor can never come up unless you wish to undo your last wish.

I wouldn't, i would let the wish happen, and as the campaign progressed or during the epilogue I would explain how strange creatures were being born around the world and across the realms. Very few would recognize them as Genasi those that do would for the most part try to send them to the elemental realm, a feat not often successful for an infant. Those who cant recognize the race will handle it differently. Those who believe it to be a curse/monster/demon/etc. will purge it from the world. Those who recognize the baby has elemental influence will return the baby to the elements, usually by abandoning them in the wilderness. Many relationships will be ruined due to perceived infidelity leading to fathers leaving, mothers despising the child and often during the at an orphanage. In the end after the 100 years only about 5-10% of these Genasi make it to adult hood, most never knowing what they are or why they were born.

"I wish no one could ever cast Wish henceforth!"

Granted, Monstrosities such as Tarrasques lose their greatest weakness, when the next on rampages, its destruction is unfathomable and its kill count immeasurable. 

"I wish you never wanted to do any of the evil things you did"

The Big Bad develops a sense or regret for its past actions. The big bad becomes a puppet to a bigger bad. The Big Bad as a mentality shift from personal desire, to Duty where they wish their was another way to achieve their goal but this is the only way and even though they dont want to the press on.

"I wish your brain signals were suddenly reversed"

Instead of See, thinking and  acting. They now Act and then think leading often to more dangerous results.

Sure, make sure you word it properly