Well it really wouldn't be a HUGE change, I disagree Alextopher.

I don't think the game would suddenly all be about towers, because the amount of towers you can have are very limited, and they would still be strongly overpowered with the right number of creeps.

What I'm going for here is a structure that can kind of help around everywhere else when its got nothing to attack or repair

I love programming/working with towers, and I love that they can do more than one thing. I do, however, find it odd that they can repair AND attack yet they can't help build things or upgrade a controller.

I think this should be changed and that tower should serve a more multi-purpose job since it wouldn't be a HUGE change, and they would still be limited by time and being fueled. I don't think this would change a lot, but it would provide the player with more strategic freedom. I'd personally like to use my single tower to upgrade my controller from a range if hostiles aren't detected.