The only lenses I have that will give comparable fields of view on each camera are a trio of f4 zooms. They aren't ideal - ideal would be three Zeiss Otii of different focal lengths, with the mythical perfect adapters. Not only do I not have 100mm,85mm and 55mm Otii lying around, the right high-quality adapters would be very difficult to come by (Canon or Nikon to Sony, X and GFX all exist, but the only one that I know is available from a major brand is the Sigma adapter from Canon to Sony), and there is a question of whether the 100mm Otus would cover the 33x44mm sensor (some full-frame lenses do, and that one seems a reasonable candidate).
What I ended up with is the Sony 24-105mm f4, Fujinon XF 16-80mm f4 and Fujinon GFX 32-64mm f4. They were all available, and they have a significant overlapping focal length range. Would I prefer to use really good primes? Sure, if I had them at focal lengths that matched field of view - the zooms will make that much easier! There really aren't that many sets that would work - the only two I can think of where all three lenses more or less exist are (23mm, 35mm, 45mm - actually exists) and (55mm, 85mm, 100mm - almost exists, but the medium format lens is a slightly too long 110mm). Would I prefer to use zooms with less range on the smaller sensors (24-70 and 16-55, for example)? Again, that would be ideal, but I was limited to what I had on hand or could borrow. Fujifilm chose the 16-80 (as well as the 32-64 on the GFX), and they really like that lens. The 24-105 is the normal zoom I happen to own for the Sony.
Besides the zooms being good lenses, but not always great ones , the other problem is that adjusting for depth of field is hard. Either the APS-C lens ends up wide open OR the medium format lens is in diffraction territory. It needs 1 stop between APS-C and FF, then another 2/3 stop between FF and medium format f4, f5.6, f7.1 works, but the poor APS-C lens is wide open. Probably the best compromise is f5, f7.1, f9. The medium format lens will be diffracting a little bit, but not badly...
Dan