After much research, I have decided that I should aim to build a moving-gantry, 3-axis mill, with a 2′ x 4′ bed (sized for a 1/4 sheet of plywood, although I will only be able to use about 20″x40″ of that as cuttable area).
There are several sets of plans for machines online:
buildyourcnc.com
DIYLILCNC.com
JGRO
Joe’s
… I have decided to build against the buildyourcnc plans.
The infrastructure will be of 3/4″ hardwood ply, with NEMA-23 size stepper motors. The rest of the electronics kit is TBD.