i was planning in doing a fortress map after i finish with the ones i started but since you came up with the same idea i might as well give you some info on what i was planning.
here is the image i planned to use. don't mind the perspective i wanted a top-down view.
so the key and center point of the map would be the fortress
in front and on the flanks battalions of troops trebuchetes and so on. in the back of the castle a mountain with a cave that connect to the castle via a tunnel. the sieging army can be split in various territories like (royal pikemen; knights; crossbowmen, etc) and the fortress is also split according to the defensive armies it has ( archers swordsmen, etc) also the fortress has several other territories (look at the image)
i also wanted to add some other things but couldn't because the current xml sistem is not permissive enough, like ranged attack for trebuchetes, moat as an impassable border that can be destroyed becoming a normal border, etc.
“In the beginning God said, the four-dimensional divergence of an antisymmetric, second rank tensor equals zero, and there was light, and it was good. And on the seventh day he rested.”- Michio Kaku