Well first problem is when you assign your controls to something else wasd keys are still being used for the handling bits, so you basically get 2 sets of controls. You can overwrite the wasd keys to something else and they will no longer function as whatever they usually do. The second part, and my real concern, is if you do assign one of the handling controls to something else if you exit the vehicle while holding the button you get stuck going in that direction. So say you bound reverse to shift and hold shift while exiting the vehicle, now you are stuck going backwards. The only real way to stop going backwards is to keep hopping in and out of the vehicle while tapping some direction, it isn't exactly consistent what direction, or completely restart the game. If you simply rejoin the server you will still be going in whatever direction you were going in.