For instance, would love to see attack bonus and AC divorced from ability scores.
Heck... I think it'd be cool if there was 'offense' and 'defense' for all three pillars of the game so that classes could be balanced with each other that way too.
In combat you have bonuses for 'attack' and 'armor class'.
In interaction you have bonuses for 'discourse' and 'morale'.
In exploration you have bonuses for 'perception' and 'veil'.
This allows you to have balanced battle for all three phases of the game. Physical/magical combat, social combat, and exploration. And each class could be assigned a total +10 bonus points to be divided up amongst the three offensive and three defensive pillars however the player chooses (with maybe an automatic +2 assigned to the primary pillar of the class).
So a Fighter might get a free +2 to the combat pillar (offense and defense.) He then divides his 10 offensive points +4 attack / +4 discourse / +2 perception and his 10 defensive points +6 armor class / +2 morale / +1 veil.
So all told his offense and defense are:
+6 attack / +8 armor class
+4 discourse / +2 morale
+2 perception / +1 veil
This character is pretty proficient in melee combat and even stronger defensively. He is fairly competent in interacting with people, but can be somewhat easily swayed. He also is not that great at discovery or understanding the lay of the land, and cannot hide his way out of a paper bag. Basically... this implies a really good warrior in very strong, heavy, and loud armor who has some personality to him. A shining knight, perhaps?
Rogues, rangers and warlocks would gain a +2 to the exploration pillar, clerics and bards to the interaction pillar, and paladins and barbarians to the combat pillar.
Granted... I realize this is complete fantasy because the game would never get deconstructed like this... but it would solve the issue of how you balance classes over the three pillars. The main downside is that there are many, many DMs who would hate-hate-hate for interaction and exploration to come down to dice rolling 'fights' rather than just roleplaying them out. Which is certainly a valid concern and one that this method I describe really can't be fit into.