Scottgee1 mentioned Pentax screwmount (M42) cameras. He wondered if Criteria #7 could be met. The answer is yes, yes, Oh yes. I have a complete kit - 3 bodies (one black, bit o' brassing here and there; yummy) and about five or six (I'll have to look) Super Takumar lenses. Killer glass on these Takumars.
Several people in the US repair, refurbish, CLA these cameras . Eric Hendrickson, in Sharps Chapel, TN,(pentaxrepairs@aol.com) is a retired former head of the Pentax repair division. He has lots of parts in stock. He has CLA'd all my bodies and they are now as new.
Only part that seems to be in ever shorter supply is the meter cell. But I think enough are out there for another three or four decades. At which point many of us on this forum simply won't care.
The Spotmatic is a small camera, not as small as the wonderful and esoteric Alpa, but as small as the new Bessaflex, also an M42 screwmount. I love these Voigtlander folks. "Hey, we got nothing else to do, let's make a brand new M42 screwmount SLR! Must be a lot of folks out there with dying bodies and healthy lenses, right?"
And they were right.