How about a digital body that looks and feels like the cameras we're used to, where we know where the controls are located and which way to turn them? It was a successful strategy when Nikon introduced the F and wanted it to capture the serious amateur and pro markets. If you were already shooting an S3 or an SP your fingers knew where to go and what to do when they got there. Leica was five years too late, made the Leicaflex the wrong size and the wrong shape, and no interchangeable finders or focussing screens were possible, let alone available. Hell, it didn't have a "focussing" screen, just a split image rangefinder in the middle of clear glass.
Within a few years the Nikkorex hit the market, allowing Nikon glass to go on a relatively inexpensive body. A much larger number of people could afford to "go Nikon",
and many pros picked up a Nikkorex body also, because the Copal Square shutter allowed for a much higher flash synch speed. Meanwhile the flagship F allowed you to buy the new through the lens metering prism finder to upgrade your camera. You could add a motor drive or even a bulk film back.
When Leitz finally came out with a full focussing screen with the introduction of the 'flex SL you could finally use a 180/2.8 that focussed the right way, no more confusion with the backwards focussing direction of your only Nikon F and its 180/2.8 Nikkor.
Then there was the camming issue with the Leica SLR's. Each new model required lenses with a different cam to tell the meter what f-stop you'd chosen. Sure, they'd add cams to your old lenses for a price. Imagine sending all your M lenses back to get upgraded to function with the latest camera's "new improved" rangefinder. Wait a minute! Didn't the introduction of the M8 cause you to send all your M lenses in to be "coded"? Brilliant!