I would allow a Maximized dispel magic. However, the only aspect that would be affected by maximization would be the 1d4 rounds of supressed powers in a magic item specifically targeted by the spell.
As for confusion and the like, I would rule that Empower Spell and Maximize Spell only affect things that are measurements - they do *more* damage, affect *more* targets and so on. They would not affect random variables of a spell that just determine which of several affects apply, such as for confusion and prismatic spray - in the case of prismatic spray they would affect the Con damage from the poison ray and the duration of the blindness effect, though.
As for confusion and the like, I would rule that Empower Spell and Maximize Spell only affect things that are measurements - they do *more* damage, affect *more* targets and so on. They would not affect random variables of a spell that just determine which of several affects apply, such as for confusion and prismatic spray - in the case of prismatic spray they would affect the Con damage from the poison ray and the duration of the blindness effect, though.