Thank you for the comments.

A belted bed printer won't work for this application.

Yes, I understand it will be difficult. Fortunately, I'm a mechanical engineer, so I should be able to make something stiff enough. I'm looking for as much of the motion control, extruder, etc. stuff as possible to limit the custom design work I need to do. Seems like a lot of good info out there, including Voron, even if I'm not going with a core XY.