I would be thankful of you discussed my proposal, not somebody else's.
Ah okay, did not understand your proposal was locked to CMOS, sorry.
With CMOS I'd say it's not a suitable time to make an open source digital back
. There is only one option which is the Sony 44x33mm sensor, and I think the Pentax offer will be cheap enough, and for those that want a detachable back the sensor is a bit smallish (for V mount or RZ), and for technical cameras it has too large issues with crosstalk to work well with technical wides. I've made quite thorough analysis of the crosstalk issue on tech wides over at getdpi.
I guess some would still like to have it, but I would personally not be too interested in the back. I'd like to hear those that would be interested in such a back what they would use it for. I'd guess for some sort of table-top technical photography. But for that application you could get an Arca-Swiss MF-two and a Sony A7r, a 36x24mm sensor is not that much smaller, and soon the 50+ megapixel is coming to that.
I think what people mainly desire in the 'MF geek space' is larger sensors for the legacy MF SLR systems (hassy H and mamiya RZ) and the Hy6, the larger sensor is needed to get the 'look' from the the format's lenses, ie large sensor area is more important than resolution, and live view is of little interest. High ISO would be nice for those working in natural light though. When it comes to tech users I think people are quite satisfied with sensor sizes but lower prices would be nice, and good wide angle compatibility is a must, which the current CMOS doesn't provide. Live view would be great of course, but without wide angle compatibility it's a no go.