While I can't speak specifically for the Olympus fisheye I did try my Panasonic 8mm fisheye in my 180mm dome set up for my 12-40mm lens on EM5 in Nauticam.
I believe that the new Olympus fisheye is longer than the Panasonic but that probably wouldn't make much difference. I removed the 20mm extension ring and mounted the 180mm dome directly to the n85 to n120 adapter and the lens was so far back from the glass dome that I ended up with the porthole look to the image. The majority of the image was the black inside of the n85 to m120 adapter and dome port leaving only a small round image through the glass dome.
Given the reported diameter of the new Olympus fisheye I don't think it would work with the n85 to n120 adapter I have as it does not have an external lock.
The size of the 180mm dome port also creates some strobe placement issues if you are trying close-focus wide angle shots (CFWA) where the subject is tight to the dome.
Truthfully I love the compact size of the 4.33" dome for CFWA but was hoping to try some over-under shots with the fisheye AND the bigger glass dome. The 4.33" acrylic dome plus wave action makes over-under very difficult with the fisheye, let alone strobes burning the corners of the images in my local plankton / sediment filled waters...