GM needing help (PF)

[Rift_Wolf]

I'm running a 10th level party, one of whom is a wordspell caster (Starsoul Sorcerer 10). I've allowed him to use this alternate casting ability despite a) I don't understand it, b) Some of the wordspells are poorly worded, and c) while he took it for versatility he seems unable to do very much beyond blasting and abusing compulsions. But he seems happy with his character and I don't want to ruin his fun. My main problem is with one of his new meta words; manifestation. To me it seems a very metagamey idea, swapping one save role for another doesn't really make much sense in-game. Also, this gives him more scope to abuse the poor wording of Complex Order (Which he has done before to commit borderline sex crimes).

I know Word spellcasters are underpowered compared to, say, a wizard, and I probably shouldn't have allowed him to use a system I don't understand, but I feel I have to draw the line somewhere, and I can't ask him to completely reroll his character as we've been playing for almost a year now.

TLDR version: Should I allow him to have the Manifestation word, or tell him to choose a different word?

[Corlindale]

I really don't see anything particularly powerful in Manifestation. Fort saves are usually higher than will saves anyway.
I don't think it's metagamey either, clearly characters in the game can have an idea of what it means to target fort vs. will - to attack someones bodily constitution or assault their mind. He just uses the power to assault the body instead of the mind - nothing metagamey about that.

As for his particular (ab)uses of Complex Orders, that might be more of a player issue than an actual power issue. It's a good spell, but I don't think it's broken.