The idea of just two classes is oddly appealing. I'd like to see an RPG based on that.
re: spells, I also would love to see the reality-breaking high-level spells dropped from the lists. (Although I suspect it will never happen because Tradition.) There's no need for anything above 5th or 6th level; at higher level you just use higher level slots for lower level spells. Sub-classes could potentially get signature "spells" as capstone abilities.
A few other things I would like to see:
1) Disentangle ASIs from Feats. Yes, yes, I know the argument about "they promised optional sub-systems" but the current system isn't working. ASIs are too good compared to most Feats, except for a couple of overpowered Feats that all the munchkins take. I want to take some of the really fun Feats but the optimizer in me can't do it. (I think about starting a campaign with the inverse rule: ASIs are outlawed; Feats only.)
2) More features in sub-classes. I'd like to see maybe 6 rather than 4 sub-class abilities, with the two new ones showing up sooner.
3) Ability score modifiers removed from classes. Recalibrate point buy if needed to give everybody the same bonuses to be used where you want.
4) New ability score generation that provides more variety and even some...gasp...randomness. (I recently suggested Point Buy for three stats of your choice, and straight 3d6, in order, for the other three. Or 4d6-1 or whatever. Something totally random.)