I had the same idea last year and tried to light up my pictures with my dive light and with a video light. I ended up buying the fisheye tray and arm and a YS90DX strobe. This is still a very compact system and IMHO the better choice.
The problem with dive lights is that they usually have a spot reflector.
If you want to go for light you'll have to order your dive light with a flood reflector or use a video light as dive light.
Using light helps the camera to focus and you have better exposure control but IMHO a lack of brilliance.
You might try to combine light and the internal flash of your Oly, this will work for macro, closeup, fish photos and reef scenes where there is something to light within one meter.
My experience with a video light that was not connected to a strobe arm and had an accu tank connected to my bc were absolutely not satifying. It was very hard to hold and focus the light in one hand and the camera in the other, trying to control exposure and focus.
If you want to have a compact setup, buy the fisheye tray and arm and try to fix your current divelight (change to a flood reflector if possible) to the arm. It really doesn't make a difference under water and it is still very compact on land or on a boat. (BTW: This is what i do for night dives now)
If you are satisfied with the results, think about buying the new dive light, otherwise buy a strobe.
Sabine
Helge Suess is using two (!!!) HID video lights, have a look at his
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