I like the idea of various viewfinder options (eye-level, waist-level, etc.). Perhaps a "video port" arrangement where you "plug in" your viewfinder of choice.
Two shutter release buttons (one on top, one on the front face)?
With regards to what Full Frame is; Is it not just a bigger rectangle
(36x24mm) and than APS-C and not square?
For an equivalent area of coverage to a Full Frame but shaped as a square, that square would be just over 29x29mm.
One thing about pixels: it is not about how many overall there are but rather pixel density (i.e. how many per mm (either horizontally or vertically)). Higher densities result in higher resolution and software written to manage the sensor signal would have to compensate for any noise factors.
Finally (for now) what about going to a CCD instead of a CMOS?
One more thing - a built in phone/web browser (an IPhone in every K3 - team up with Apple) so you can send your pictures home or to whomever wirelessly and also browse the web in your viewfinder, etc. (Iphones I find are useful for photographing my ear drum).
They might as well throw in a heating device so you can iron your tie before a meeting too.