I mentioned that I plan on using the Onstep telescope motion control system to handle motion control for this rotator

Howard, the creator of Onstep, has quite a few models available, this one is the MiniPCB v2. and the processor can either be a Teensy 3.2 or 4.  I've got a Teensy 4 in there as that's what I have.   He also has a lot of options for stepper motor drivers.  Just change the code to suit.

Limit switches are connected to the 3.5mm mini stereo jack on the bottom right.

What does this get me?  A few things.  One is, its use of an advanced version of Mead's LX200 protocol.  That means  theory at least, I could track satellites with something like kStars& ekos.  Lots of power in those two systems.