Using battlefield structures.

At present there are many wonderful looking houses/small castles/buildings on the battlemap, however it is impossible to put say a group of archers on the walls on this structure, or say retreat to the doorway of this building (thereby negating flanking).

Enabling these structures would open up new stategic options on the battlefield.
(Imagine the nasty surprise when those pesky rebels are holed up in an impressive mini-castle and you had thought , "Ill just run these guys through with my lances")