Hey, that's actually a good idea. That's mostly a precedent as far as Warband mods are concerned, and it really adds to the atmosphere.
I have a suggestion- I believe the Floris mod team created a script in which garrisons of castles sally out to attack hostiles. Since the mod is entirely OSP (I think?), you could also use that script to make it so cities can be interacted with more. For example, if you're a scriptor, you can make it so that the local town watch will help people who are attacked by bandits in the vicinity of the town.