Probably
But the walls and buildings will need a lot re-textureing.
Indeed. The closest to something medieval would be the http://images2.wikia.nocookie.net/__cb20090215235014/fallout/images/thumb/a/aa/Fo1_Shady_Sands.png/830px-Fo1_Shady_Sands.png though (by Fallout 2, Shady Sands still uses the same kind of walls). Other than that, Adytum would have a http://images2.wikia.nocookie.net/__cb20100422020053/fallout/images/thumb/f/f1/Fo1_Boneyard_Adytum.png/830px-Fo1_Boneyard_Adytum.png, Junktown would have its "http://images2.wikia.nocookie.net/__cb20090217200332/fallout/images/thumb/e/e1/Fo1_Junktown_Entrance.png/830px-Fo1_Junktown_Entrance.png" and things like that. Nothing troops can stand on, unless Boradam adds ramps and the likes to them. Maybe the towers could house armed guards, snipers, machine guns though.
Idea I had for how you get an howitzer, which is pre-war. Maybe you allow the construction of a Scavenger's Guild in your town, and they sell anything pre-war to you they can find, like the howitzers.