Hi Smiffy (Beano fan ?)
It is difficult to reply to your questions as you have joined a worrying rationale to some specific, detailed information requests. But we would like to help if we can.

If you are buying a Workbee, speak to the guys at Oozenest or post questions on the Open Builds Forum that covers that model.

If you really want feedback on your business plan, Jazz has already warned you off. Any business justification that is based on the idea that doing it yourself will pay for itself from saved sub contract costs either means 1) You are failing to include your time into the costs 2) You have failed to get the right price from your subcontractor 3) You have no idea what is involved. So for your business the spec of steppers is the least of your problems from what you have told us.