Probably be easier to start with an old one and rehab it. There are so many old ones out there that I don't think there is much market for an assemble-it-yourself. Although with a CNC router and a little time, it wouldn't be too hard to knock out a kit....maybe when I retire (:
Like Daire, I also made a foam core camera that could be easily adapted to wood. It is based on the one shown in Alan Greene's book Primitive Photography (I think?):
I also rehabbed a Calumet C1....it really wasn't all that hard, but I have a ton of images to help out others who want to do the same:
I'm hoping to start on a hybrid Eastman/Deardorf/carbon fiber Frankencamera this winter. I'll post the result if I ever get around to doing it!