It was not unheard-of back in the film days. The cameras, like the Fuji GW690, were not exactly small, but you could carry them around on a neck-strap and use them without a tripod.
Leica has already a medium format camera (S) with interchangeable lenses, its super expansive but a medium format Leica with fixed lens for (example) 9000$ I think would sell really a lot.
Also a Sony medium format for 7/8000€ would sell a lot (more than Leica surely). We’ll see...