Backscatter may have an existing adapter for that purpose, can't say for sure. If you measure the OD of your GS VF then I can tell you if it fits in the Aquatica's VF opening. As for Zoom Gear, Aquatica has 2 gear sizes, the Series 1 & 4. Which housing are you wanting to use, I can see about measuring it for you. Basically, all current housings use the Series 4 gears, older ones use Series 1.
Sony is APS-C, not m43. I have the NEX-6 as my walkabout camera with the Sony 18-105 and just love it. If the A6000 is housed, I'll be getting one. I can easily get a Metabones EF adapter to use my Canon lenses.
If anyone in the Portland, Seattle, Vancouver Area are interested in a touchy feel-y experience with the new Aquatica AE-M1 housing. We will have one on display at the SLS Photography Booth (No.812) at the Seattle Scuba H20 Adventure show this weekend!