It's an interesting idea... though rather a lot of work. For a start, there's the AF screw-drive, aperture control and EVF to add in. That would take up quite a bit of space and have greater power requirements, so a bigger battery would be necessary. I doubt they could keep the GRIII frame - they would need something bigger.
A more realistic option, IMHO, would be to take the KP, remove the mirror and PDAF assemblies, shave off the mirror box, reposition the aperture control, and fit an EVF where the existing OVF is. All of which sounds quite straightforward, but it's actually a significant redesign requiring (I'd guess) lots of new components
EDIT: The design, prototyping, testing and tooling would, I believe, cost no less - in both time
and money - than another DSLR to continue Ricoh's chosen Pentax path...