This is probably a stupid idea to most of you, (and it may already be a function of forts in game) but I was wondering if it's possible to modify fortifications so that they cause a movement penalty for vehicles and infantry passing through them. The idea being some fortifications are built with tank trenches, obstacles, etc. The movement penalty could be negligible at lower levels, but would incrementally increase as more levels are built, maybe close to swamp or jungle movement at level 10? If it's possible, it seems like it could be pretty easily, but I just don't know how.