eelnoraa
Contributor
The diver determines if they are positive or negative and then adjusts the amount of air in the high pressure bladder. This is NOT an automatic servo-system.
It may best be described (as one of the commenters called it) as "variable static buoyancy."
I think Chris has it spot on. You have lack of understanding about buoyancy. The fact that driver needs a BC is because the overall buoyancy changes as the dive progress. Either by the change of weight of your gas, or exposure suit buoyancy change .... . Throughout the dive, the diver needs to determine his/her own buouyancy and adjust accordingly. In your system, it seem the diver still need to adjust his/her buoyancy, but this is not done once, but throughout entire dive, which effectively random your system useless. I think the assumption that once adjusted to neutral, the overall buoyancy doesn't change much throughout the dive is fundamentally incorrect.