Nice details Frank.
Indeed D600 is a very good camera.
D600 - Angenieux 35-70/2.5
The D600 cuts it IQ wise, the D500 is much better in AF and (sic!) MF too
plus all the fifth gen goodies like color consistency over a huge range of ISO and light sources.
So what we need are two more full frame fifth gen cameras:
a D780 = a D600 in a D500 body (transcending the D600) and
a D850 = an A7R2 in a D500 body (transcending the D810)
PS: even with the FM-2 on furking film I can still see the superior IQ of the 4/300PF compared to the 1.4/35 Ai-S which is still a super great performer.