If this thread is open for more or less crazy ideas, I have one.
I haven't given up on a thin camera that keeps the K mount.
The problem isn't really the K mount itself, but the registration distance of 45.46mm caused even the thinnest film SLRs to be about 50mm (like MX or ME Super). With sensor, SR system and LCD todays K mount DSLRs are more like 75mm thick.
But there may be a way around this. A thin Pentax EVIL with a mirror. A fixed mirror.
If a fixed mirror is used to reflect the picture upward to a sensor placed where the focus screen are on SLRs, the registration distance will no longer determine the camera thickness. Give the mirror a good SMC coating and the picture degradation should be minimal, place it behind the shutter and the mirror will not have more dust problems than the sensor. Some advantages:
-Thinner camera body
-Include the mirror in the SR system and correct motions with both sensor and mirror. This should help cutting down the difference between in body and in lens SR.
-And with a mirror that can shift a bit thanks to the SR system, everyone of your lenses would be a shift lens.
-The DA ltds fit right on without adapter and makes this packages super small.
-All current and passed K mount lenses fit directly without adapter.
This would at least be different.
The less modest version (with interchangeable viewfinders) you can find on my blog.