This is a complex problem, but here are some ideas:
Those born prior to 1988* will receive social security payments as expected. Those born prior to 1988* interested in opting out of Social Security may do so, thus relinquishing benefits aside from certain incentives. Appropriate incentives would be determined by committee.
SSI, et al. will no longer be a federal program and will be handled individually by each state.
Those born after 1988* will be removed from the system and offered tuition assistance equal to the amount already paid into social security, to attend technical, undergrad, or grad programs. Private retirement for those born after the decided year will become mandatory.
*TBD. Different levels of incentives to opt out could be offered depending on the decade of birth.