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.
I am using Hedwig's flash trigger successfully with the EM-1 and a whole bunch of different strobes (Inon and Sea & Sea). Works like a charm BUT you will need to mess around with the LEDs on the trigger to get them to flash only in the window.
In SOCAL I shoot the sealions with an 8 mm Fisheye (EM-1) in a small port system. Manual flash and 1/320 shutter (sometimes 1/250) at f11 or so. Before they show up I set the f stop to get the blue that I want to see then wait for them to come in close. You are right they are zooming along but with that setup you can get a fair percentage of keepers.
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.