I like that idea. What if the rogue doesn't get a normal expertise dice progression, but rather all of his maneuvers require a skill check, and succeeding grants you, say, 1 die plus 1 per 3 points by which you beat the DC? The dice would start at 1d4, and every even level the rogue chooses one attribute and increases the die size used with that attribute by one?
Sneak Attack might be a Dex + Bluff check against an enemy's AC, so a rogue who rolls an 18 against a target with AC 12 gets +3d4 damage, or +3d8 at 5th level if he chose to increase the die size of Dex-keyed maneuvers at both 2nd and 4th level. A trip attempt might have you roll Str + Sleight of Hand, and if you succeed by 3 points you send your target stumbling 2d4 feet before they fall prone. And so forth.
Combine that with someone's suggestion earlier in the thread to give the monk a per-encounter ki pool that he can use to roll expertise dice with a certain cap per round to differentiate the monk from the rogue and fighter, and that would make the fighter the regular, consistent combatant with his expertise dice allocated at will each round, the rogue the flashy, spiky combatant with his "expertise dice" determined by his skill checks each round, and the monk the impressive, methodical combatant with his expertise dice rationed out each encounter.
I think it would work pretty well, yeah. Some more interesting manuevers wouldn't hurt either, though.
Also, I wonder how the rangers and paladins would fit into this scheme. And speaking of rangers, I'm curious as to whether they'll keep being shoehorned into two fighting styles or not.