just make a I/O button for individual track stop, just like we have for airplaine gear brakes.
Throttle and steering would be the same whether you are gunner or not, with steering going from js in driver position to rudders in gunner position as it is now.
Turret Yaxis wouldn't have to have a remote control from the driver seat, but Xaxis would be a boon.
Static rotation of tracked GVs could be done by just pushing throttle fwd, pushing the break-torque button on the side you want to stop, either that or the invert-torque button, and the GV will have the fwd-going track going fwd at the speed of your throttle, and the other either stopped or going backwards at that same speed.
If some GVs had both inversion and break of track torque, then you need three buttons avail for each. (left-brake, right-brake, invert.)
Gunner steering with that setup could get a little hairy, but only because it'd improve on a simple setup, and wouldn't be any harder than what we have to coordinate in planes.