Only the 50'0'c doesn't have changable screens. I will certainly keep the 50'1'c in mind in case this 501 c/m doesn't work out. And indeed above 120 mm wouldn't be the logic lens on a Hasselblad.
I am a bit puzzled about the numbers though, but once you feel you have to start checking numbers than it's probably no good at all. I will follow my heart on this one, that always results in the best pictures so probably in a good camera as well