Fewer classes? I'd push for a classless system if I thought anybody'd listen to me. There has to be some way to balance this idea, but please hear it out (if you can still hear it over the sound of sacred cows dying in excruciating agony): No classes. The same xp model. All things that are currently class abilities, feats, skills, additional HP, etc are all "purchasable" with xp. Costs are assigned to each ability so as to make them balanced and not overly succeptable to mad min-maxing. You start out with a set number of xp to create your character, and as you adventure, you earn xp with which to purchase new abilities or improve old ones. You keep a running tally of total xp, to determine what "level" you are for purposes of xp rewards and CR comparisons. No, really, this could work! If you don't limit your character to one or two areas of specialization, effectively creating your own class, you end up good at nothing, just like over-multiclassing right now. But it's the ultimate in customization!
That's what I'd like to see. I don't think it's going to happen, though.