So for users this means they have to spend 21000 gas per year to keep their account active and if they fail to do so they have to pay for a witness proof.
Do you have a ballpark of the gas used by a witness proof?
If miners are required to store the current epoch and the previous epoch, and all contracts and accounts used at least once per year are in both the current and previous epoch, wont that make the amount miners have to store 2x the total active ethereum state? If so, then if the active ethereum data * 2 is greater than the inactive ethereum data, then this change would end up increasing the amount of data miners have to store.