Owning a KP and a K-5 (but not a K3), I'd suggest the ergonomics of the "front e-dial/shutter button/DOF Lever" arrangement of the two cameras are sufficiently different to be "annoying", (if not downright inconvenient)!
For me, switching between two bodies in an action situation, I'd much prefer to have the button layouts as similar as possible. The *ist's, the K-5, the K-70 (and probably others) are all very similar, why they had to change things on the KP I can't figure
Even the very slightly different placement and feel of the shutter button can be sufficient to have me thinking twice on occasion ... I find it a nuisance!
The KP is a jolly good camera, with lots of advanced features, but if I've got to think about where to find them whilst my subject is disappearing into the next parish I'd rather have a second body I'm totally familiar with