I knew the TS-Es would work. But I was very surprised that the Canon 200mm f2.8 L II worked perfectly on the GFX. No disturbing vignetting. Sharpness on the GFX is better than the same lens on the 5DsR across the frame - even in the corners.
The TS-E 17 and 24 work very well too. Shift is a bit more limited than on the 5DsR, so you've got to know your lenses really well. The T-E 90mm has a more limited image circle, but alllows some shift too. My PC-Distagon 35mm does not show the desaturation it does on the 5DsR with full shift in the corners (maybe a bit, but not much).
I started working with a mixed system for my architectural work two weeks ago. Two cameras using the same lenses - GFX and 5DsR with these lenses: TS-E 17mm, 24mm, 90mm, PC-Distagon 35mm, 200mm 2.8 L II. Will soon be accomplished by the TS-E 50mm and the new TS-E 90mm L. Gives me a row of shift lenses with 14, 17, 20, 24, 29, 35, 41, 50, 71, 90 mm + 164 and 200mm without shift.
The results so far are amazing.