I dont think there should be 'capturable' buildings, but more like advantageous landscapes, such as a rock ledge from where a batallion of archers could rain death on the enemies below, the position offers no benefit other than strategical, being higher it means a bonus to range and LOS and makes them harder to hit... It shouldnt affect the existing physics, they shouldnt 'gain +10 armour' or such for being in the location as seen in many games...
I really love this notion. It is my opinion that terrain should play a large part in strategy. Just make sure that the player is finding strategies to fit the terrian, not terrain to fit the strategies.