Yes I think a mini view cam would be useful. However it needs a lens line. 90mm image circles for a 24x36mm sensor would be overkill, but the Rodenstock Digaron-S lens line which has 70mm image circle would be a good match (always thought 70mm is a bit smallish for 44x33). With current Sony CMOS we probably will get bad crosstalk issues on the wides though.
For longer lenses people are already attaching Sony A7r to existing view cameras, like the Rollei X-Act2 or Arca-Swiss MF-2. There's a risk that since the sensor won't handle wide angles well a digiback won't provide more features than just attaching an A7r.
If you could provide a sexy (sort of) integrated system, camera and all, something that looks like a mini alpa or a mini techno that would certainly sell a few I think, but that's not as realistic I think.
When CMOS sensors are say 50+ megapixels there's another challenge, it will be very difficult to make a camera with movements that is precise enough to serve such a small imaging surface (mostly parallelism). For tech cams up to 4x5 I think the reduced precision requirements on the camera itself (meaning you have less issues of blurry sides due to too low parallelism or lens sample variations etc) is the largest advantage of larger imaging surface, rather than look.
But again everything is easier for tabletop photography, parallelism is much less of an issue when you work with short DoF, and you won't need wides. But as said, who's going to attach a 36x24 tethered digiback instead of an A7r in that case?
