A tank is literally suicide.
Your character will never win a fight.
If you post a tank character, I'll accept it.
But I'm telling you now.
You will never win.

Any intermediate character can fuck up a tank. Literally any.

There are so many more possibilities than having a guy in a tank.
Hard Science Fiction can give you a fuckton of possibilities.

Seriously, I can cough up five ideas in the amount of time it takes me to write this explanation.