I agree on this. I don't believe RAI was "too good" to be implemented, I think it was "too bad". Because, if you can pull off such a complex thing as having npc's act on a need>means to satisfy the need>action basis (I assume this was the real RAI that was supposedly "toned down"), I don't see how it would be rocket science to add some SCRIPTED components that would guarantee that the game CAN"T be broken by npcs.
Are you afraid the quest npc's will kill each other? Make them immortal to each other and mortal to player. How hard would that be in terms of programming?
Are you afraid that one npc will buy all the potions in town? Make the vendors stock refilling periodically (wait a min, that already was the case, so where's the problem if one day you enter a shop and need a healing potion and the seller doesn't have one, this is real life economy, you come back tomorrow or try some place else)
Are you afraid that some hungry and moneyless npc will start killing everyone in town for food? What are guards for then? Have him arrested! if you need him for a quest you ask people in town and they'll tell you he's in jail.