Well I'm starting to think about a project idea, I wonder if you can see any pitfalls.
I have an extra 300mm lens, a Boyer APO, that I was going to use to make a box camera. Then I thought it would be nice to have an 8x10 enlarger.
I'm inspired by a gizmo that made Polaroid prints from 35mm slides, a fixed focus box. What I'm thinking of doing is making a simple box that would be sized to do 16x20's from the full frame 8x10 neg. Sort of shaped like a pyramid. Light source would be my 9x12" light box.
I'm thinking that I wouldn't need a condenser because I wouldn't be projecting a long way. Diffusion style light. No moving parts, except maybe some thumb screws at the base to adjust fine focus. Slide the neg in the top, slide the paper in the bottom, expose and process.