Limited wish is a seventh level spell and polymorph other is a 4th level spell. Considering the limitations of limited wish - namely that you can mimic any other spell of equivalent level pertaining to your spell type list (arcane vs. divine - assuming no specialty), and the other limitations on casting spells that you would normally not be able to cast, I would allow the player to do this.
I reason it through like this:
1.) limited wish allows the character to cast ANY spell of 5th level or less.
2.) polymorph other is only a fourth level spell
3.) the only thing that is to be changed about the spell is that it now can be an outsider as well as a nonoutsider
4.) the casting of limited wish is not even being used to cast the modified version of polymorph other, but simply setting a condition for the next casting of polymorph other.
There are a few things to consider as well as reasons why this might not be balanced.
A.) I would not let this effect last beyond one round/level - this would not be able to be a dual contingency/spell modification spell - that would be too powerful. However, I might let wish do this.
B.) I am not familiar with the host of outsiders available - if this became a gross powergaming tactic, I would make sure to be fair and let all of the villians use the same tactics on the PC, as well as introduce roleplaying consequences of such actions.
C.) I already have a house rule that mandates the caster of any polymorph spell must be intimately familiar with any creature the polymorph spell will mimic. This means 1.) a one time successful role of the appropriate knowledge check (nature for normal animals, arcana for magical beasts, planes for outsiders, etc.) with the DC set to the result of an operator applied to a combination of the CR and HD, 2.) having seen the creature at least once in person, 3.) when polymorph is used it mimics that exact creature, not the average one of the species (this could mean an adjustment of CR and HD affecting both the spell and the DC of the knowledge check). btw - this has many ramifications for roleplaying - especially if the original finds out about the polymorphing (aka disguising). Also, I typically have ramifications if the caster has not gotten permission from the creature to polymorph into it. This house rule tends to temper my judgement on the spell as I have not really decreased its power, simply the ease with which that power is attainable.
D.) IDHMBWM and forget the description of polymorph any object. If that version of the spell does allow for polymorphing into an outsider than this application of limited wish would be overpowered.
