Sounds like something an Arguino Nano could do. The stepper only needs 5V.
Maybe you can cut down on the wiring by having a second Arduino act as a server to an on mirror client that can switch among the drivers or L293s.
All you'd need is a switch box to adjust the secondary. Do you really need control of all three adjusters. I'd think two should do like the early Meade 2080.
