One of the control designs for older tanks:
it should be easier to map it on gamepad than on keyboard. Perhaps some of the buttons can be used to get separate brake inputs for left/right.
Older tanks bring up something that I didn’t planned from the start - separate gearbox for left and right track.
EDIT: I know that WW1 tanks and some tanks made in-between wars, were steered by braking left/right track separately, so they were loosing power in turns. Were there two sets of gearboxes on WW2 tanks? Two gearboxes sounds like needlessly complicated even for military hardware.
EDIT2: I’ve used this article as a reference before. So there were transmission with two separate gear boxes: