It may sound tempting to just "remove AoOs and anything that relates to them". But that won't work without a complete overhaul of the entire system including classes, unless you are willing to throw game balance overboard.
For example, Barbarians, Nomads and Pirates have the Mobility chain that revolves mainly around AoOs: first it improves defence against AoOs, then later it lets them avoid AoOs altogether.
So if you take AoOs out of the game, these three classes get... NOTHING. They are better at avoiding _nothing_. So they are put at a disadvantage against all other classes that get special abilities which don't revolve around AoOs. Of course you can think up a different boon for them, but that's exactly what I'm talking about: you can't just say "No AoOs in our game" without having to tweak the whole system.