I personally think that rubble should not have obstruction boxes. For example, you have just destroyed a portion of a wall, and you want to move your troops into the enemy base, but you'll have to wait 10 seconds until the rubble is gone... that doesn't sound funny
I've been really busy this days, but here's new update. Another fortress sketch attempt. I'm not really sure if the starting layout I thought is working, so maybe it's time to start drawing some sketches before modelling. I'm not an awesome drawer but I think I'll save time and work this way. (render with AO) Anyway I think it's time to focus on the texture instead of designing... ^^