What is better for precision? Stepper motor VS DC Motor
I would have to go with a servo motor. Possibly on a worm gear driven rack and pinion. The servo control system, I would include absolute positioning sensors, (opto wheels) so that the motor control optic wheel is fallows the steering wheel optic wheel with precision. I wouldn't recommend a potentiometer as a command potentiometer, because of mechanical failure and dust might interfere in its future operation. I would also include limit switches so that the motor travel of the wheel never causes mechanical damage.