After going through a bunch of the xml and looking at monster behavior, and reading the .98 changelog there was one AI monster and bandit behavior that I would love to see, Pillaging. This would be the ability of certain CreatureTypes, think Trolls, Dragons, Bandits, given the ability to extort money and possibly materials off of the player as well as the ability to attack a town but leave it intact and potentially kill a few population points, demo a building, take money, mana and materials.

For Instance it would be really cool for Dragons, if your build a city within say 10 or so squares from his lair, would eventually send you an ultimatum, pay him in gold/materials/items/population (sacrifice a virgin or two) or he will pillage your town taking even more resources and causing population and building destruction.

Maybe moving within so many squares of a troll causes them to send you a msg demading money or they attack.

Bandits that do everything to stay alive and well hidden and specifically target caravans and undefended towns for pillaging.

Maybe even use diplo points to make deals with those creaturetypes only to harass specific enemies,etc

You could take this pretty far but just putting in a pillage ability and adding the data elements to the xml to with flags for pillaging Towns / Caravans as a priority and a "stayalive" flag would make the environment more alive.