Yeah, the controller part has already been investigated and solution found.
Going with g2core (the official successor to TinyG) for software, running on an Arduino Due with a custom made stepper board. The custom made stepper board wasn’t actually all that hard, once I figured out the right approach. Doesn’t need anything super special, as it’s not a “production run”. Instead, just manually soldering the right bits onto perfboard works fine. Tested already.
I need to circle back and get the mechanical bits sorted next, to get a full end-to-end iteration working. But, some stuff has come up so it’s been delayed.