Hey, nice project! I really like the game controls, they are really smooth and snappy. It bugged on the 2nd mission but here's some feedback anyway:
A better draw distance would be nice. I don't know if you want to keep it short in purpose but I would consider it.
The maps could use more variety. It would be nice if there were destructible props around that your tank can just run over. also I wouldn't mind different terrain types that affect the tank's movements.
Destroying cities is a bit of a chore, and I don't mean because there's 4 of them. I find myself just destroying the turrets and then slowly shooting down with missiles everything else, it's not very fun. Maybe make sturdier turrets and make some buildings that can just be trampled over.
I like that bullets are more useful for small enemies and the missiles are good for intercepting big ones but still bullets are a bit underwhelming, maybe it's just how they look.
Besides pickups I feel it would be cool if you could choose a weapon config before you start a mission but I don't know what you have planned. A hull repair pickup would be great and so would be limited weaponry like you mentioned (mines, rockets). Maybe those could go on the B button? Would you find these when destorying buildings or from killing enemies? I'm not gonna suggest weapon stuff or this post won't end.
I could mention a ton of things about the designs and art for the game but I'm just gonna nitpick on a thing that bugs me: the smoke clouds not having shadows haha
Anyway, I get excited when I see the potential of new games, best of lucks to you man, I'll be following your game!