Dynamic Balancing already exists
This is interesting because the ability of a flywheel to store energy is already proven.
Something that deforms will tend to balance if it can deform far enough.
4x4 guys are using dynabeads to dynamically balance tyres that are covered in crap, and it can react to a change in the state of the tyre too.
Maybe manufacture a flywheel with a hollow section so they can use beads to balance the wheel?