I voted maybe doom, let me explain.
I was thinking about throwing something like this into the mod, so if you want to work on it, awesome. But just so ever odd wile a goblin or 2 will come around the city for whatever reason and try to get in, so the guards will kill them. Probably mostly at night, since goblins like their dark places and night is just, the attack time, its a law of the universe. Also i wouldn't make them just attack in 3 hour intervuls os something, but make it more of a random occurance. It should be a treat to come to town to find the guards fighting, or looting the courpses of a few fallen baddies. I say goblins because they seem like the mischivious type to me.
Ps. Wolves and stuff already attack