I recommend finding a stepper that can be manually turned when not powered if you want to do some unplugged visual as well as AP.
I have a Starizona MicroTouch on a FTF that works beautifully for AP, but has to be fully removed if you want to turn the focus knob manually for unplugged visual use - plus it requires the fine focus knob to be removed.
I also have a Moonlite motor that overcomes this issue with the use of a slip clutch to easily disengage motor - and at least I can keep the fine focus knob on other side.
My favourite design, however, at least from a versatility view point is my Avalon FOCS stepper that can be rotated manually when not powered ie simply unplug or switch off power. Plus it uses a belt to drive focuser knob so I don't lose use of the fine focus knob if I want to do some visual.
So if you can find a motor like theirs for your system, then it will be good for both AP & visual:
http://www.avalon-instruments.com/pr...e-focuser-focs