You're a seventeenth level wizard and you want to have the spell wish cast. In that case, the only limit to casting wish, in current rulings, relates to the number of your willing and compliant 13th level wizard associates. Of course, this willingness would need to stretch to the extent that they'd undergo a stressful need to rest before spell casting again, a temporary period of physical weakness and a possibility that they would lose the possibility to be able to themselves cast wish even if the managed to attain a 9th level spell slot.
The current, most relevant, optional ruling, as used in Adventurer's League, states: "You Are You; and So Is [S/]He. If a simulacrum you have created casts wish, both you and your simulacrum suffer the stress associated with casting the spell—including the risk of being forever unable to cast wish again. The inability to cast wish extends to any simulacrum you create in the future."
However, in some cases a third party may potentially become involved but, as DMs will typically control the actions of third parties, I'd imagine that this could be fine.
A 17th level caster would know that, if they cast wish themselves (for an effect other than to replicate a different spell), they would suffer stress with various manifestations including facing a 33 percent chance of not being able to cast wish again.
And this is where a seventeenth level wizard may abuse/strike a deal with some of their 13th level apprentices/friends.
At 13th level, a wizard can cast the 7th level spell Simulacrum to, "... shape an illusory duplicate of one beast or humanoid that is within range [touching distance] for the entire [12 hour] casting time of the spell. The resulting duplicate ... can take actions and otherwise be affected as a normal creature... [and] uses all the statistics of the creature it duplicates,... [but] lacks the ability to learn or become more powerful, so it never increases its level or other abilities, nor can it regain expended spell slots."
The duplicate lasts until it is fatally damaged or is dispelled but, in the meantime, it could serve in a variety of functions. It's not in the rules but, given a difference in experience levels, a DM might judge a duplicate had a chance to become self-possessed and to then say something to the effect of, "I want to be a real boy". In any case the duplicate could potentially act as an able advisor/mentor for a less experienced wizard and would at least start with a 9th level spell slot suitable for the casting of wish.
Another optional ruling, as used in Adventurer's League, makes a slight further modification to the simulacrum spell description (which says that a "duplicate ... can take actions ... as a normal creature") with the ruling: "No Copies of a Copy. Simulacrums can’t cast simulacrum, or any spell that duplicates its effects.
Given the opportunity, a 13th level wizard can personally recast simulacrum but according to the consequence that, "If you cast this spell again, any duplicate you created with this spell is instantly destroyed".
Material costs: The casting of simulacrum, as a 7th level spell, requires material components including a powdered ruby worth 1,500 gp. With a wish, for example, "you can create ... one object of up to 25,000 gp."
Opportunities knocked: If, by astounding fortune, a 17th level wizard happened to have 100 13th level wizarding associates all willing or at least compliant to take on the 33% risk, then, on average: 33 of the 100 would lose ability after a first casting, leaving ~67 potential casters, ~22 of the ~67 would lose ability after a second casting, leaving ~45 potential casters, ~15 of the ~45 would lose ability after a third casting, leaving ~30 potential casters, ~10 of the ~30 would lose ability after a fourth casting leaving ~20 still with a potential to cast wish. A single 13th level wizard could enable, on average, the casting of, (100+67+45+30)/100, 2.42 wish spells and still have around a 20% chance, given their own progression in experience, of being able to cast wish in the future.
Of course, it would be easy to expand on the existing Adventurer's League ruling to say something like: "You Are You; and So Is [S/]He; and so is the original entity that you duplicated" - but this has the potential of dragging in potentially unwitting third parties into the mix and this might be done either by friends or enemies.
A potential wish caster may potentially have a friend, at least of sorts, who really liked them. In fact that friend might like them so much that they'd like their own copy. All it might take is for the potential wish caster to do something like go into some kind of hibernation or trance and the sort of friend might gain an opportunity to make a simulacrum. The friend of the potential wish caster would have effectively have acquired their own potential to cast a wish.
It may also be possible that a potential wish caster has an enemy and it might even be possible for that enemy might have the ability to cast even just one wish. (Perhaps this second potential could even come from an item with at least a single charge). If a potentially targetted potential wish caster could be approached by creatures/characters that included an enemy or traitor and if, say, that creature/character had a charge in an item that could cast wishes then, among the things that such a creature/character could do in such close proximity, would be to create a simulacrum of the potential wish caster.
Presumably, the casting of wish to create a simulacrum would require a verbal component with equivalence to saying something like "simulacrum". However, we might not necessarily need to presume that this verbal component would need to be spoken in common or that, in all circumstances, the target would necessarily be able to hear or heed it. Even if the targeted wish caster then turned to see a version of themselves standing, potentially naked and with no arcane focus in hand, and if they didn't have other things to do at the time then, yes, it might be easy for the potential wish caster to cast something like dispel magic. Of course, the targeted wish caster might necessarily know that the naked figure was not a more minor form of illusion but, if choosing to take chances, the simulacrum's life could be very short indeed.
However, if the simulacrum survives, can be communicated with and can, indeed, cast wish (or could even use counterspell) then, if all these conditions are met, it could be useful.
Casting wish would put the original potential wish caster under stress. The wish could be something along the lines that the original potential wish caster couldn't leave or that s/he/it would have increased vulnerability to necrotic damage. Even if the potential wish caster did manage to leave (without having dispelled the duplicate first) then newcomers to the scene would have an albeitly stressed replacement ready to stand in place.
Under current rulings there still ways by which high-level spell casters may access an increased number of wishes but in ways that would, in one way or another, involve NPCs. Additions to current rulings could have a potential to affect creatures inc. characters against their will.
You're a seventeenth level wizard and you want to have the spell wish cast. In that case, the only limit to casting wish, in current rulings, relates to the number of your willing and compliant 13th level wizard associates. Of course, this willingness would need to stretch to the extent that they'd undergo a stressful need to rest before spell casting again, a temporary period of physical weakness and a possibility that they would lose the possibility to be able to themselves cast wish even if the managed to attain a 9th level spell slot.
The current, most relevant, optional ruling, as used in Adventurer's League, states:
"You Are You; and So Is [S/]He. If a simulacrum you have created casts wish, both you and your simulacrum suffer the stress associated with casting the spell—including the risk of being forever unable to cast wish again. The inability to cast wish extends to any simulacrum you create in the future."
However, in some cases a third party may potentially become involved but, as DMs will typically control the actions of third parties, I'd imagine that this could be fine.
A 17th level caster would know that, if they cast wish themselves (for an effect other than to replicate a different spell), they would suffer stress with various manifestations including facing a 33 percent chance of not being able to cast wish again.
And this is where a seventeenth level wizard may abuse/strike a deal with some of their 13th level apprentices/friends.
At 13th level, a wizard can cast the 7th level spell Simulacrum to, "... shape an illusory duplicate of one beast or humanoid that is within range [touching distance] for the entire [12 hour] casting time of the spell. The resulting duplicate ... can take actions and otherwise be affected as a normal creature... [and] uses all the statistics of the creature it duplicates,... [but] lacks the ability to learn or become more powerful, so it never increases its level or other abilities, nor can it regain expended spell slots."
The duplicate lasts until it is fatally damaged or is dispelled but, in the meantime, it could serve in a variety of functions. It's not in the rules but, given a difference in experience levels, a DM might judge a duplicate had a chance to become self-possessed and to then say something to the effect of, "I want to be a real boy". In any case the duplicate could potentially act as an able advisor/mentor for a less experienced wizard and would at least start with a 9th level spell slot suitable for the casting of wish.
Another optional ruling, as used in Adventurer's League, makes a slight further modification to the simulacrum spell description (which says that a "duplicate ... can take actions ... as a normal creature") with the ruling:
"No Copies of a Copy. Simulacrums can’t cast simulacrum, or any spell that duplicates its effects.
Given the opportunity, a 13th level wizard can personally recast simulacrum but according to the consequence that, "If you cast this spell again, any duplicate you created with this spell is instantly destroyed".
Material costs:
The casting of simulacrum, as a 7th level spell, requires material components including a powdered ruby worth 1,500 gp.
With a wish, for example, "you can create ... one object of up to 25,000 gp."
Opportunities knocked:
If, by astounding fortune, a 17th level wizard happened to have 100 13th level wizarding associates all willing or at least compliant to take on the 33% risk, then, on average:
33 of the 100 would lose ability after a first casting, leaving ~67 potential casters,
~22 of the ~67 would lose ability after a second casting, leaving ~45 potential casters,
~15 of the ~45 would lose ability after a third casting, leaving ~30 potential casters,
~10 of the ~30 would lose ability after a fourth casting leaving ~20 still with a potential to cast wish.
A single 13th level wizard could enable, on average, the casting of, (100+67+45+30)/100, 2.42 wish spells and still have around a 20% chance, given their own progression in experience, of being able to cast wish in the future.
Of course, it would be easy to expand on the existing Adventurer's League ruling to say something like: "You Are You; and So Is [S/]He; and so is the original entity that you duplicated" - but this has the potential of dragging in potentially unwitting third parties into the mix and this might be done either by friends or enemies.
A potential wish caster may potentially have a friend, at least of sorts, who really liked them. In fact that friend might like them so much that they'd like their own copy. All it might take is for the potential wish caster to do something like go into some kind of hibernation or trance and the sort of friend might gain an opportunity to make a simulacrum. The friend of the potential wish caster would have effectively have acquired their own potential to cast a wish.
It may also be possible that a potential wish caster has an enemy and it might even be possible for that enemy might have the ability to cast even just one wish. (Perhaps this second potential could even come from an item with at least a single charge). If a potentially targetted potential wish caster could be approached by creatures/characters that included an enemy or traitor and if, say, that creature/character had a charge in an item that could cast wishes then, among the things that such a creature/character could do in such close proximity, would be to create a simulacrum of the potential wish caster.
Presumably, the casting of wish to create a simulacrum would require a verbal component with equivalence to saying something like "simulacrum". However, we might not necessarily need to presume that this verbal component would need to be spoken in common or that, in all circumstances, the target would necessarily be able to hear or heed it. Even if the targeted wish caster then turned to see a version of themselves standing, potentially naked and with no arcane focus in hand, and if they didn't have other things to do at the time then, yes, it might be easy for the potential wish caster to cast something like dispel magic. Of course, the targeted wish caster might necessarily know that the naked figure was not a more minor form of illusion but, if choosing to take chances, the simulacrum's life could be very short indeed.
However, if the simulacrum survives, can be communicated with and can, indeed, cast wish (or could even use counterspell) then, if all these conditions are met, it could be useful.
Casting wish would put the original potential wish caster under stress. The wish could be something along the lines that the original potential wish caster couldn't leave or that s/he/it would have increased vulnerability to necrotic damage. Even if the potential wish caster did manage to leave (without having dispelled the duplicate first) then newcomers to the scene would have an albeitly stressed replacement ready to stand in place.
Under current rulings there still ways by which high-level spell casters may access an increased number of wishes but in ways that would, in one way or another, involve NPCs.
Additions to current rulings could have a potential to affect creatures inc. characters against their will.