I would NOT ban abjuration... other wizards become too dangerous then...
necromancy is a good one to ban for an evocation specialist... you don't need to level drain them, they are taking hundreds of damage :)
As for illusion... what are you missing out on enchantment?
A lot of things have "immune: mind effects" which make them immune to the entire school of enchantment... those same things that are immune to enchantment often AUTOMATICALLY FAIL any save against an illusion school spell.
The biggest loss with conjuration is the ability to teleport IMAO.