Gantros: my DMs typically don't tell me the AC of what I'm attacking. So doesn't this undermine the time-saving practice of pre-rolling? In your system, I have to ask if each attack hits and by how much.
I have my issues with Gantros' solution (though they are slowly eroding) but I am going to back him up here-- tangentially.
One of the things I mention in in my advice for speeding up play is to dispense with the "AC is secret!" mentality.
My players are smarter than the average bear-- well, mostly, except for the fact that they can't add up bonuses quick enough to suit me. But they add them up between rounds, and they keep notes, and so within about 3 rounds they have the monster's AC pegged to within a couple of points, anyway.
(EDIT: Tangential note. I expect my players to do this-- what I did not expect was that the ringleader behind these careful meta-gamey notes was the LARP'er chick at the table. We're going to miss her, and her "I
rage, and I
shift, and I power attack for everything I can!"-- graduate school stole her away from us.

)
Just dispense with the false suspense: Tell the PCs what the AC is.
The gain you get in a smooth running game far outstrips the benefits of "secret AC."
Shoot. You're right. Maybe that's a good feat to design then, which at least limits the access to monsters.
Two very quick comments, admittedly without a lot of thought behind them:
1) I have no problem with PCs being able to do things the monsters can't, and vice versa.
2) There are existing feats that are similar-- Superior Cleave (Oriental Adventures) lets you take a 5 foot step after you drop an opponent. I could certainly get behind a similar feat-- or, frankly, a blanket permission-- that allows a fighter to move after dropping an opponent, provided he has not moved yet. Basically, allow you to break up your full attack at any point, with one move, provided that such movement wouldn't otherwise provoke an AoO.
But not attack -move a bit - attack -move a bit more - attack, etc.
Hmm... The levels of success method breaks such a solution. Gantros, do you allow the attack multiplier if the combatant has moved?
And while I am thinking of it, do you do anything different with multiple attacks? (Claw/Claw/Bite routines and the like.)