I have no idea what type of game you were trying to make. If you wanted to make a realistic tank sim - you failed. If you wanted to make an arcade tank sim with realistic elements - you've succeeded.
The main reason I'm saying that is a fairly low TTK on enemies (at least during my playthrough) and insane speed of the tank. Tried doing the cyberdemon strat on one of the enemies and was surprised to see that he tried tracking ahead of me (he later stopped for some reason, maybe tower speed is not fast enough). Anyway, speed is king, and run-n-gun (or drive-n-gun) strat seems to work wonders.
Destructible models are really cool, especially when your own tower gun gets bent. I got a heavy WoT vibe from it.
I have no idea how effective the turret is since I had most of the fun with the main gun, and the damage feedback from it is way more apparent than from turret.
The only thing that stuck out to me is how barren the levels are. They are pretty much almost flat desert arenas, which are pretty boring once you run out of enemies. But I assume those are not the final levels.
Anyway, I really enjoyed what you have here. Please keep it up!