I suspect the size of this sensor to be entirely prototypical. Despite being an avid photographer since 15 years back, with all the market insight accompanying

I suspect the size of this sensor to be entirely prototypical. Despite being an avid photographer since 15 years back, with all the market insight accompanying that, I just can't see what market segment an interchangeable lens system with a sensor size between M4/3 and that of a pocket camera would be aimed at. Does anyone know of any long-lived system from any manufacturer with a sensor of this size? There are a few novelty models out there, but they never seem to catch on, always resulting in a single camera model with just a few lenses, disappearing from the market soon after.