It all depends on the final gearing. But, you'll have to have the power off, as already noted. Why not build a clutch/gear drive. Simply use 2 drive gears the same size, but with the clutch disk,(under spring tension), inbetween them? That way you can move the focuser manually. Won't you get similar focus adjustments/pre-set settings with a belt drive system?? The electronics look good.
L.