Hmmm, I've been trying to resolve the same sort of nagging problems in the game I run; when I ran 2ed combat seemed to move much faster and more fluidly, and now that I run 3ed I'm trying to figure out how to regain that dynamic and still keep much of this ed's combat options.
So far I've done this:
No AoO's except if a combatant is trying to cross a cohesive enemy line, or when a combatant rolls a critical miss (which means it is very likely their foe will gain a free attack, but other untoward things could happen), ... or, I had been trying to decide whether or not to keep the casting-provokes-AoO rule.
This thread has gotten me thinking along the lines of having all movement actions occur at the same time and all standard actions occur as they fall in the initiative order. . . hmmm