Why does one want FF?
In film era, 35mm seemed to be the best balance point - satisfying IQ, affordable, portable. This is not necessarily true in digital era. FF IQ may be better than APS-C, but by how much? What about other factors? I think people would agree that all of CNSPO find APS-C is currently the best balance point. From this perspective, I don't see why users really want FF.
What does one want FF for?
Does he want to pursue ultimate IQ? Does he have a lot of FF lenses that he wants to fully utilize? For the first purpose, he's got to spend money & get an MF DSLR. For the second purpose, he has to realize there exist DA lenses with eqiv. FOV & equal/better optical quality. On top of that, Pentax allows him to use all old lenses (better than CN). To many people, APS-C IQ is good enough.
Who really wants FF?
I think most FF-favor people have 35mm film camera background, probably with a long history. He either has accumulated some 35mm lens stock or has thought 35mm as golden standard. If you ask someone who started SLR hobby directly from APS-C, he may not have the same strong belief.
What's important - letting Pentax satisfy my desire or letting Pentax survive
I have some expensive film-era Pentax lenses that I too want to fully utilize their potential. FA31, FA77, Takumar 17mm, 645FA300mm are some examples. However, I realize their fortes on film may never be able to repeat in DSLR. I would rather to support Pentax (by buying APS-C DSLRs & DA lenses) to let them survive so that I can keep using my old lenses as well as new ones.
What's the big deal to stick to Pentax?
If one really wants FF, the best bet probably is to get CNS (just post his Pentax gears here in marketplace
). But, IMHO, Pentax is more considerable to their users than other brands - that's one of the reasons why they stick to APS-C.