No, but...
If you duplicate a spell effect and the save DC that comes out is for a 7th-level spell, then it seems to me that the effect you're getting is a 7th-level effect. (And thus not suitable for contingency, ring of spell storing, etc.)
But Limited Wish also says it can "Produce any other effect whose power level is in line with the above effects". It seems like you could just wish:
- "I wish that my contingency spell should get a casting of reincarnate plugged into it."
- "I wish that my ring of spell storing should get a tongues spell plugged into it."
- "I wish to meet the 'imbue with spell-like ability spell' prerequisite while magic item crafting today."
I think all these effects are "in line" with the original power of duplicating spell effects.
The spell's school is whatever the duplicated spell's school normally is
The basic use of this spell is to duplicate any other spell...
Duplicate here mean to "make or be an exact copy of". Note that the wording says the entire spell is duplicated, not just its effects. An exact copy of a spell means that it is identical in every aspect, which includes school.
If wish was intended to only take some of the characteristics of the spell and not others it would say so. In fact, it does say so, but only for two specific things.
Wish specifically indicates things that are not duplicated from the spell
You don't need to meet any requirements in that spell, including costly components.
Wish tells us that only one thing is different casting a spell using wish versus casting it normally: requirements of the spell do not need to be met.
...The spell simply takes effect.
Also, it is implied by the wording "the spell simply takes effect" that wish also overrides the casting time of the duplicated spell.
Since no other exceptions are noted the spell should be treated exactly as if the spell had been cast normally including duration, range, school, etc.
Wish only lasts for an instant
Wish is an instantaneous spell which means no matter what it is gone the instant after you cast it. But say you used wish to cast a spell, say geas, on a creature using wish. The instant after wish is cast the only effects remaining are going to be of the spell it is duplicating not wish itself.
Wish conjures a duplicate of another spell
Essentially, it seems that using wish to duplicate another spell would result in the casting of a conjuration spell with an instantaneous duration which then results in another spell taking effect with all the details that that spell has (including school). Wish conjures the other spell into existence and then disappears leaving only the conjured spell's effects.
Best Answer
Its not really that powerful
You can get geas as spell-like ability or even supernatural ability by worshipping Besmara and becoming one of her Evangelists, which should be available as soon as 12th level. This turns geas into a standard action:
So, for a skill check against a fixed DC of either Diplomacy (for out of combat) or Intimidate (for combat situations) with a DC of 10+HD+cha bonus, which you can obtain a fairly high bonus by 12th level, especially if you are a cleric or oracle, which already benefit from a high charisma.
If you compare that it's a 1/day geas as standard action at no cost, to using a limited wish for 1500 gp, it's much cheaper, and trust me, this isn't something new or unique to Pathfinder.
Limited Wish is vastly more powerful though and the fact that it can make spells that normally have a long cast time into standard actions is already proof of it's power, but that's not a problem with geas, it's a problem with limited wish (and wish). They are very powerful spells.
But if you look at what a wizard can do at 13th level, you have several very strong options too, from disintegrating the target to turning them into a frog, to commanding a group of people to kill each other, to traveling to another plane mid-combat. At 13th, you already have Power Word: Blind, which can nullify most humanoid enemies at that level, especially spellcasters. A lot of encounters ended quickly after a Wave of Exhaustion, or Greater Black Tentacles (black tentacles is a favorite of mine playing a wizard).
The fact that it doesn't allow a save makes geas powerful, but not as powerful as you think, its a subjective effect that can be subverted if you are not careful with your wording when casting the spell. Saying "kill all your friends" will suddenly be met with "f--- you, I'm not your friend anymore" phrases for the duration of the spell if your players are clever enough. Thinking about it, I would have serious doubts about the sanity of anyone saying they are still friends with someone who is trying to kill them.
Keep in mind that the cheapest protection from compulsion effects is a 1st level spell (Protection from Alignment), which won't help if they are already under the effects of the spell (which allows no save), but will prevent geas from working on an already protected target.