I woulodn't mind scrapping the Wizard entirely in favor of the Beguiler, Warmage, etc. What does having a do-everything caster do for the game, anyways?
I wouldn't go quite that far, but I wouldn't object to doing to Wizards something like what was done to 3.X Psions. All Psions specialize in a Discipline- I'd like to see an end to the generalist wizard, and make them all Specialists.