This is sage advice. You can do MFD on the cheap, but not too cheap.
IMO, unless your just in love with an older blad, or RZ, AND you can shoot in a less than pressured production, older digital takes a lot of work.
Like T and his blad, we go through the same thing with our Contax(s). I have 5 bodies, 5 viewfinders, double the lenses and out of all of that, including yearly service, I have two fully working systems, the rest are sketchy, and keep in mind contax was one of the few film cameras that was born with a digital interface and doesn't require cords and third party adapters to make them work.
The one thing about the Contax is the Zeiss lenses are always sharp and fast and have never required calibrating.
Given that if/when I buy a new MFD for professional work, I personally would look at it in two ways.
If I wanted to spend less and didn't have to worry about tethering I'd go with the Pentax, if tethering was important I'd go with the new H5d.
AT 7 grand the Pentax is virtually the same costs as my Canon 1dxs with lenses, if you shop legacy the lhe costs is less than the Canon.
The H5d40 is obviously more expensive, about double the costs, but with tethering, removable finder, software suite and in lens shutters does twice as much.
BTW: The H5d auto focuses better than any medium format camera I've ever seen. I mean it just snaps to the point and holds and does it quickly, almost 35mm quick.
I spent about 45 minutes trying to fool the focus on the h5 and rarely could. The H5 really is a refined version of the earlier H series.
If your not shooting for direct commerce I can understand using a camera that you like, regardless of the work or usability, but in the long run, the newer cameras in almost every format are very good.