Would this be tier 0?

[Doug Lampert]

I'd say ability to change game rules can make a class tier 0. I.e. if that class can remove limitations on Wish, or bonuses stacking, change class abilities and feats other characters or monsters have.
So if a class has Manipulate Form as class ability he will be tier 0.

+1
Manipulate Form is stronger than tier 1 and exists in the game, if a class gave something equivalent it would be stronger than the tier 1 classes.