Boy, some people certainly seem to get sensitive when someone talks about their 645Z cameras.
Face it, the 645Z is a terrific camera but it is the leader in that market segment. As such Pentax has been able to set the expectation.
That is not true at all in the full frame market. There is already a lot of competition and a lot of expectations. Whether you like it or not full frame cameras are primarily categorized by price. Higher price, higher expectation. If you expect to be taken seriously in this market then you better play with the big boy and price your goods in the vicinity. And the specs better be impeccable if you want to draw people away from their Nikons and Canons.
Of course you can always go off and try to build your own market segment like Sigma with their Foveon cameras.