Why would you want the FM3 with AF if you want to use all those MF lenses?
I'm not sure a company would do that, are these MF lenses even made anymore? They won't make much money from lens sales if everyone just buy the body and go on eBay to get their lenses.
The catch 22 with these compact FF camera is that you want all the modern goodies with the small size.
You either create a whole new lens line up or use an existing line, like Canon, but that's also insane as that defeats the purpose of a compact FF in the first place.
Personally, small FF, a few 24mm to 100mm primes in between, all wide apertures and be done with it.