A very interesting thought. Perhaps it would not be a "big" manufacturer. There are many companies making "niche" products.
If there were such a thing, what type of mount would you suggest it have? Perhaps a recognized SLR mount (even one not today very popular), on to which various kinds of adapters could easily be fitted?
I would suggest the shortest possible flange focal distance instead of using any of available mounts + making money from selling adapters for other mounts. Sell it as an open platform and marketing the adapters as fast and safe so one adapter would be for one lens.
Leica builds cameras for vintage MF lenses. What do I have to explain? A large proportion of their rangefinder lenses were designed in the 50s-60s and they are all MF.
But is a bit too old school (technologically): no IBIS, no sensor cleaning, no good EVF, optical finder doesn't work with adapted lenses, price. They look good but as a tool I would imagine something else these days.