I'm using ACE with HLE and Duel - Combat Realism. Really, really like it, although I might have to do some testing, because two-handed weapons seem to be completely overpowered both for me and enemies. You said you wanted AI changes and ACE + Duel delivers pretty well, I think. I especially like Duel's new NPC AI when sneaking -- they'll no longer go "oh, a dead guy, must've been the wind" but will instead go into search mode and come looking for you.