What I have thought about, when looking at the old patents to find the angles and dangles for the reflectors, is the majority of the camera body requires very little precision, at least not for prototyping.
A large plastic clsmshell with a mounting pad, then a holder assembly with precision turnscrew adjustments.
We'll need three film backs, also with some kind of 3-point adjustment for planar perpendicular adjustment. But the 3 film gates can be rough with the precision limited to the mounting plate.
What I was sort of hoping would materialize is a community effort - and I nominate Chris as the librarian - to put together an Open Source Hardware Project. Hopefully one that will live on well beyond all of us into the future.
I suggest the project name K-15, as the successor to true three layer color process using B&W emulsions.