The answers have been helpful to understand what current issues exist and why Pentax may not consider it as the best idea. I can also understand why people who appreciate extensive customizable buttons and good ergonomics may not want to straddle along a Pentax KP successor, just for looks.
I think K3 Mark III form factor is great. A KP form factor would impact the whole DSLR experience. Either Pentax should make a truly retro and thin but highly capable mirror less lineup, or they should continue making their excellent DSLRs. A juxtaposition of both might be more Frankenstein than cute.
I don't really understand nostalgia for old technology. I mean, I understand it if it's an object one bought a long time ago and kept preciously, why not, but I don't get why one would want something new with a look (and often bad or limited ergonomics and features) from the past.
I mean, if it's a passion for very simple cameras with stripped down controls, one can just buy a GoPro ? :-D
In this shrunken camera market, there seem to be only two ways to survive - compete to be the best or offer something different in a niche. There's a third route too - connect to the internet and bring an Android like open platform for cameras that allows third party app development and quick sharing. But Japanese companies are obstinate in not pursuing this so I'll disregard it.
Competing aggressively with CanikSony is a ship that sailed long ago for Pentax. So the other option is niche, which they already do well for DSLRs. I'm obviously not asking for a full replacement of DSLR lineup with mirror less. Just make a one line of simple full frame camera that is 24-30 Mp and six or seven small primes - 23/35/40/50/75/90. Like those small Voigtlanders.
Even a small company like Voigtlander has diversified from just M mount lenses to other mirrorless manufacturers, and now they even make APS-C lenses specially for Fuji.
Classic design has worked well for Fujfilm and Olympus Pen(E-P/PL) series. Classic design actually fits well with ergonomics of small primes. It is only with larger lenses that problems arise.
We also must see why manufacturers moved to mirrorless. Because it saves them money. It is actually much easier to make mirrorless cameras, compared to making a custom pentaprism and aligning the mirror etc perfectly. It makes cameras lighter, less complex, and latest sensors are fast enough to even forego mechanical shutter.
It takes very little extra R&D for Pentax to pull this - they have a production line, 90% of parts are same, an EVF can simply be bought from a vendor and the software already has a lot of features from other mirrorless cameras. If Ricoh GR can be successful, maybe a Pentax MILC Lx can be as well. But I guess it is not Pentax engineers but Ricoh management that ties their hands.
Pentax might have to look for another owner if they have to reinvent themselves(again!).