I don't like the specialist school/prohibited school thing. It is too cut and dried.
I would like a mechanic where the specialist does not get more spells per day, but instead gets, say, hmm, example:
An 8th level Evoker ("prohibited" Enchantment/Illusion, with 18 Int) can use his 4th-level spell slots to memorize Cone of Cold, Displacement, and Suggestion. Thus you get that boost in your favored school, and a penalty in two other schools, but you don't run into the mind-boggling "prohibited school" idiocy, and of course your specialist really *is* better at his school than the plain wizard.