Best bet would be to add an aftermarket focuser to the back end and fit a motor to this .
No need to go as far as Moonlite et al , the Skywatcher SCT focuser is a fine beast for a modest outlay , handles a DSLR with ease , and the Skywatcher Autofocus motor can be fitted to it.
You can also add USB control to the motor (various options available) eliminating the need to touch the focuser by hand and control it from the laptop.
Coarse adjustment can still be achieved by using the original knob moving the mirror as before , independent of the rear focuser.
Yes it adds a little to the back end but nothing to worry about , my HEQ5Pro has no issues with the set-up.
The whole lot can be detached simply by unscrewing from the visual back if required.
http://www.opticalvision.co.uk/astronomical_accessories-focusers/dual_speed_2_crayford_focuser_for_sct_telescopes.html
http://www.opticalvision.co.uk/astronomical_accessories-focusers/skywatcher_auto-focuser.html