DRJ
Hedonist
One solution I believe RiFE had was Fort Commanders; units tethered to the fort but able to deny the enemy its usage. They were simply garrisons that prevented say a scout from walking in and taking advantge, though they obviously wouldn't be able to fight off a significant army themselves.
fort commanders like town watchmen? I think that's a good idea, to program the town watchman/guard to see forts as towns so the ai would put them there, too. Also, the unit could get the 50% bonus for the town on fort also - is this possible to code?
being at the topic: another thing about forts is that if the player put them on their borders (and some well promoted units in them the ai doesn't seem to try to invade anymore... anyone else experienced that?