A fun twist on the TD formula. I quite enjoyed this game, and it's well executed.
I do think there are some small things that could be improved from a user experience perspective, for example reloading towers that aren't out of ammo, or how you can reload a tower then pick it up while it's reloading, but you can't reload a tower you've picked up. Also, you can get stuck between enemies and buildings and be unable to pick up your tower. However, I think that this concept has a lot of potential to grow beyond a simple game jam experience.
Also, bomb towers are useless, imho. Maybe buff their range?