Both AOI and Ikelite have surprisingly-compact, and surprisingly-cheap, housings for the mkii. Ikelite is now selling TTL units which work with the housing, as well as vacuum kits.As to ports, it just depends. You can use the Panasonic 8mm fisheye with a 4” dome, very wide of course, but surprising for close work also. I assume you have the 60 macro, which takes a flat port which isn’t too large; my Nauticam port is threaded for wet optics and I assume the Ikelite is also given the popularity of super close-up optics. You’d likely want a second strobe if you use the fisheye, but the results can be great.
having the fisheye and the 60 leaves out a lot of range, of course. A go-to lens for Olympus users is the 12-40 pro. With Nauticam kit, it requires a dome, which as you note is big and heavy. Given the popularity of that lens, Ikelite or AOI may support it; however, the 12-50 “kit” lens gives decent results.
if you’re happy with your Mkii these seem like options worth exploring In addition to the Olympus housing.