I had an idea for destroyable buildings. Basically you would have an indistructable roof, foundation, and vertical supports at each corner of the building. None of these parts can be destroyed. But the actual walls of the building would be like the collapsable fencing used around the army bases in OFP. So say you have people hiding in the building, you could blast the wall down with an RPG, or tank shell, or just ram the wall down with a tank.