I don't think anyone has a TTL flash trigger for the u4/3 cameras and it is not clear that the Nauticam trigger will fit in your housing, check this carefully. Getting an LED to drive TTL is not terribly simple for optically triggered strobes. As you know typically TTL is obtained by the internal strobe sending out a weak signal then measuring the resulting intensity then sending out the true strobe signal. Neither Olympus nor anyone else has published the inner workings of their TTL (except in some difficult to understand patents) so this is tricky.
Clearly Bokeh is subjective but for me the Leica/Panasonic wins. We were just in the Northern Sea of Cortez and I shot a lot of brown cheeked blennies with both lenses in similar backgrounds, will try to post some later today.
I have and shoot both. In my opinion the Bokeh on the Panasonic is much better than on the Olympus but the 60 is slightly sharper and focuses slightly faster for me (EM-1, Subal Housing). Neither are hard to handle in my opinion but neither are as simple as a 60 on FF. In terms of macro both lenses shoot 1:1 so the magnification (i.e. the macroness) is identical for either lens although adding a diopter to the 60 will get more mag than the same diopter on the 45.
Think about strobes for WA. The S2000 has a GN of about 20 and the YSD2 has a GN of 32. This sounds like a lot but in reality it is only one stop or so. NO strobes can light up a reef or a whale shark and any strobe can give you good CFWA stuff. WA photos are really about natural light and getting your composition correct.
For the s2000 with a GN of 20 (in air) or say 7 in water this means that
GN = Distance (meters) * f stop
so 7 = distance (meters) * 11 (for f/11) so we can light up something about 2 feet (0.63 meters) or so away
with the D2 and a water GN of 11 we can light up the same thing one meter away at f/11
so the D2 is only good for an additional foot of distance.
For a strobe with a GN of 20 (meters ISO 100) on land, I would estimate a GN of 10 (or less) underwater. If I want to shoot at f:11 then I can be around 0.9 meters or a bit less than 3 feet away. That is why (even with strobes) the rules about get closer and closer are what they are.
The 105 Nikon lens has a minimum focus distance of about 1 foot (30 cm or so) measured from the focal plane line on the camera body (not the front of the lens). At that distance you get true 1:1 i.e. a beastie 36 mm or so across fills the frame. What you should do if you are interested is to mount your camera on a tripod and shoot a ruler at various distances from the ruler and you will see that even relatively large movements away (say an inch or 10%) you will still get 38 mm or so filling the frame. If you play that way you will find out how important (to you) that last little bit of magnification is.
I have shot with the canon 60 and adapter. What I do is set the focus long before shooting; and use the manual move the camera forward and back to get the shot. Works fine if a bit slow. Trying to use autofocus with any of these adapters (so far) seems hopeless.