Looking at the map again, I just had a small thought about strategy that I think you have to incorporate. The tower is so tall that it needs stabilizing cables down to the ground, but that makes those stabilizing cables a massive weak point for the defensibility of the tower itself. After all, the only thing a rogue driver with too many points on his license needs to do is go to one of those anchor points and place a small bomb, then the next gust of wind will blow the DMV over. I think therefore that you need to put some little earthworks and gun emplacements around those anchor points as well. Nothing big or ostentatious, but enough to let the would-be drivers know who's boss.