Variation 1 shows the possibility of replacing part of the mass with flexible mooring lines (as shown below by special springs). This would help keep the structure from swaying off in one direction or the other and it would help keep the structure level.
Buoyant Energy Animation Option 1
In turbine operation mode the structure is lowered in a controlled motion and energy is released. In pump operation mode electrical energy is converted into potential energy and stored while the whole structure rises against gravity.