No, if there's nothing keeping me from ganking the wizard then I'm ganking the wizard the instant he or she reveals himself or herself as a such.
If every monster acts like Seal Team 6, what do you do (outside of powering up the monsters) when you want the party to fight Seal Team 6?
I would say DMs making every monster a Patton, is just as pervasive, and pernicious as making all monsters idiots.
That said, NO AOO. I've ran about 4 different playtests with 7 different people, all whom played lots of 3e and at least some 4e, (and some lots of that as well), and everyone has commented on liking not having AOO.
I must admit, I did experiment with "Readied Reactions".
Basically at the end of you turn, you can ready a reaction.
Thus the Fighter rappeled down a cavern ledge, shot a Kobold with the crossbow, and then pulled her Axe and readied an " I attack anything that comes next to me".
If something triggered the reaction, the corresponding action was used on their next turn. Thus if the Fighter above killed a Kobold out of turn, their " Action", would be gone on the next turn.
1 reaction per turn, still applied, and I did not allow for permanent initiative order changes for interrupts.
For something I made up on the spot, it kept people engaged even when it was not their turn, and allowed people to detail their "attack posture" at the end of their turns.