Sven,
I don't know about using the 105vr w/the dome, it would seem to me difficult/impossible; but then I'll let someone else with more experience answer that.
But I can give you my practical experience with the newer Subal 105vr port (dedicated - w/manual focus).
Good thing is the port is really nice and the manual focus knob on the port contacts the manual override on the lens very smoothly. Manual focus is nice and relatively easy with that port.
Drawbacks to the Subal 105vr port are:
It won't fit the 105vr lens plus a diopter (say a 5T or 6T) inside. I have a question on this myself on another thread - but it seems to me if you add a small extension ring to accommodate the diopter then the manual focus that contacts the lens directly (no additional gears on the lens) - won't line up? I haven't worked it out yet as I don't have an extension ring yet, but I'm trying to work this out and have ?s out on it in another post to see if anyone else has.
Also the Subal 105vr port is very wide, about 120mm, so if you want to put a Woody's diopter (wet & removeable underwater) on the end you will have to get a special size. I thought I had a source to get me one but the dealer never delivered after many inquiries from me so I contacted Woody directly and he is putting together a wet diopter in the size cap to fit the 105vr for me, his service is great. Maybe some smart people here could figure out how to put his wet diopter in their own larger cap (I think there was a post on it), but I'm not that bright...... 
The 105vr lens and the 105vr port are heavy, but then you probably already have some buoyancy solutions worked out as the whole d200 system is heavy. Plus I'm sure as far as the "diopter" thing you could add the backscatter MacroMate to the Subal 105vr port, they have one in that size, but the MacroMate lens is very heavy underwater on an already overly heavy lens/port/camera system.
I think you can get Subal extension rings for the 1.4X and 2X different size teleconverters to fit and I don't see then any problem with the manual focus knob on the Subal 105vr port aligning with those added. Still I'd be interested in anyone's experience with TCs and diopters with the newer Subal 105vr port. There have been threads on similar things but not much regarding their use with this dedicated port.
That's what I know.
Best, Carol