Definitely a good idea.
IMO when you are placing a turret you should see a very transparent sphere/cone (and surfaces in it would be slightly different colored) and the bright (or inverted color) line where it intersects something for all offensive structures. Also, if something is in the way, we would need to know only where the turret shoots from.
Another possibility is to make lines extending from that point until they intersect something, that would also show (with which areas are closest to acid(which has damage based on distance) and how likely a trapper hits a moving player.
Building is currently very poor IMO and could be heavily improved.
BTW. how did you make the screenshot with damage boxes, Oblivion? That should be in options.