Ok so hear me out...

Instead of requiring that employees pay into Social Security, the State requires that this amount be converted into bitcoin sent to a time-locked address that YOU hold the keys to, that is locked until whatever the "retirement age" was when you started employment.  Different potential timelock per new employer.  Each employer pays to a different address all derived from a single xpub.

If the State really cares about forcing people to save for retirement, this is a much more efficient model and you always hold the keys to your own saved money; no opportunity for it to be rehypothecated, redistributed, or spent by the State, and you get exactly what you were forced to save.

Note: Not an endorsement of State force.