Oo. I think it just dawned on me how you are describing it. The pump and such are in a WTC, separate fromt he cuff. The cuff is in a ballast tank (doesn't even need to be sealed... or a tank, just contained in the sub), when the cuff inflates the water is forced out, when it deflates, water makes its way in.

As long as there is enough air to inflate the cuff from the WTC, yes i see it working.

I was mainly having issues with displacement vs air volume... Displacement is what will bring the sub to the surface, not the volume of air in it.