I wouldn't. Until the shutters have been serviced, they're not a serious camera any more, for somebody interested in doing consistent work.
This argument doesn't sound quite convincing to me. As you mention, even relatively modern camera will be of unknown precision until serviced/measured.
It would be relatively easy to make sure we get reliable exposure of one of these old cameras. Like:
- Have it serviced
- Get a cheap shutter tester
- Make a DIY measurement with a digital camera shooting through the old camera body
- Or simply do some test exposures using cheap film with different aperture/shutter speed combos.
What can't be solved is the color rendition and contrast. A lens from the 50s will never be able to get colors as vibrant as a modern one, and it can't be corrected for in post production.
In this respect the Mamiya C220, specially with the later lenses will give much superior results than a 50s folder, and be sharper too.
I used one for quite a while and the image quality is superb.