Upload & Sell: On
FF digital square format (i.e. 36x36) rangefinder with convertible 100% optical viewfinder.
Hey, you did say "dream" ... it just needs to use a split mirror (perfect with split prism or gridlines screen) that "pocket door" slides apart to reveal the sensor. MLA for rangefinder use, mirror together for critical TTL viewing.
By using the sliding split mirror, you negate the longer registration distance needed for the mirror to 'flip' up out of the way. Thus, you could use a registration distance like the M series, and would be able to mount everything from M to FD/FL to EF to F to M645, etc. via adapters. No more need to rotate orientation for portrait/landscape, etc.
Leica ... are you listening.
I'll trade you design rights for production models.
Leica ... are you listening