I guess you are one of those handful of photographers I am talking
about. What percentage of the DSLR buyers do you think you represent?
Ah, but that's my point. That's why there doesn't need to be a cheap affordable Digital MF camera, or even for Pentax to make a FF Camera. There isn't a big enough market for high-end expensive digital cameras, to allow Pentax to compete successfully and to make a profit and make it worthwhile to themselves and their market. Get a decent APS-C camera and some decent lenses. I enjoy photography for fun and pleasure and my own artistic and fun projects, so I have that side of me as well, I just got back from 5 months out of the country with just my DSLR . And for that side of me, APS-C (my K20D) more than meets my needs, I have a couple DA*zooms, the 55-300 and the 3 FA Ltds. Great lenses. That's why I bought back into Pentax for DSLR. In fact I still have a fair number of Iris inkjets on my walls that were made from back when I had a Canon 3MP DSLR.
But I firmly believe that for this larger percentage of DSLR buyers that you speak of do not need more than APS-C. Whether it is Pentax K20D or Canon 50D or Nikon D300. All excellent cameras if you outfit them with decent lenses. And these are affordable cameras that fit perfectly into the market you speak of and fit perfectly with me as well. It's a mysterious discontentment that would make one feel that they needed or had to have a digital FF or digital MF camera, unless in order to book work or keep jobs they had to have one.
I also firmly believe that while Pentax did once make a decent (after a few iterations) 645 Camera and sold it at a reasonable price. The R&D and materials and selling point price and profit margin allowed them to do that. This is no longer the case and the much more expensive and intensive R&D required for Digital MF along with the materials and the construction (even in the Vietnam) will end up with a camera that is out of the price range and usefulness to those who make up the Pentax market.
Pentax will best serve it's customers and the market the best by continuing to refine its APS-C camera. There's a lot of improvements to be made here first and foremost before deserting all its customer base for the ego of chasing Canon and Nikon and Mamiya and Leaf and Leica and Sony or whoever.
Refine and perfect the K-line of APS-C. Improve the AF accuracy and speed, add some more AF options, put a better buffer into the works to allow faster frame rates, solid state memory is so cheap now. More metering options, color metering. Better processing engine with improved signal to noise ratio, genuine 14-bit or greater throughput. They can take what they have and while everyone else is chasing MF and FF, Pentax could improve their K-line APS-C into the best one on the market, with little additional investment (compared to from scratch FF and new lenses for FF or MF and new MF lenses) And finally get busy with more lenses, more primes, get the DA*30 finished up, add an 85 and 135 and 600 and a newer 11-16, perhaps a 135-300 or so.
I think everyone who currently shoots Pentax will be happier and have a better end product if Pentax did this, then go out and try to go down the FF or MF road, with the cameras being ok, but needing a few model releases over the next few years to iron out all the kinks and 3 to 5 years worth of lens development before either FF or MF has a comprehensive set. I know that a lot of people think that, OK Pentax has FF and 645 lenses, so it's good to go. But FF shows up a lenses deficiencies more than lower resolution and smaller sensors, so if a Pentax FF comes along, even the FA limiteds will not look as strong or stellar as they did on APS-C or film. You think there's some PF and CA now with them? wait until you pop that onto a FF digital camera with 21 or 28 MP. Even mores so for a MF high res sensor with the older 645 lenses. Those lenses were never as strong to begin with as the Mamiya or Hasselblad lenses, and if those older designs were put onto a new 645D, they would never, ever be able to compete with the other makes.
Pentax got a late start on a serious DSLR, and it hasn't quite caught up with the entire line yet, as is evidenced by the lenses still on or not yet even on the roadmap.
Let Pentax complete and perfect what it is in the middle of doing, and let other makers make other makes. Then maybe down the road, think about adding something else.