Well, well. I couldn't help myself. I was thinking about an easy compromise between fixed focus and the semi-hassle involved in modifying a helicoid. Lo and behold, there's an obvious solution:
Use a folder with sliding focus. That way you can set the focus anywhere you want.
I removed the lens/shutter from an ancient Zeiss Cocarette and mounted the Agulon 65 from my other
DIY camera in a downsized lens board. I just used a random metal ring I had lying around to make the hole smaller. If the original retaining ring had not been so tightly stuck, this operation could have been done in minutes.
I'll shoot a roll and see what happens. It seems to focus down to 30 cm, so I'll do some extreme close-ups for ya one of these days.
Did I forget to mention that it folds? So this is basically the DIY-in-minutes-pocketable-lightweight-wide-angle-MF-camera. Not bad.