Of course you could use the M lenses. Software could make the corrections, as the camera will already be able to recognize what lens is mounted due to the 6 bit coding.
And Leica already has a menu selection where you can manually pick the corrections for whatever non 6 bit lens is mounted.
Software is the answer, why are you hung up on physical limitations? It's already being used in the current Ms!
Leica will do this, because it will kick start the M sales. I see zero reason to update my M240 for a new M that is the same bloated size. It already takes amazing pics.
But if they reimagined the M by making it's size comparable to a film M, oh my.
It can be done.
Or you can pretend it is impossible, the way people accepted the limitations of the M8...