This is my gripe with a lot of 645 cameras too, fine if you take mainly portrait photos I guess.
Yes, at least the 645 SLRs are the `right way round', but bulkier and awkward to use vertically without a pentaprism accessory viewfinder. The Pentax looks better than most in that respect.
If I was still using medium-format I would try and find a nice Mamiya 6 and get the rangefinder and lenses calibrated. For a one-lens system, I have fond memories of a Rolleiflex 2.8GX, which had a convenient built-in meter and great lens.
With moving subjects I think one really needs to zone focus with these cameras, and rely on depth of field. Though I have never tried the medium-format autofocus systems, I imagine they would be slow from that era.