To get a handle on the total debt market, one must consider how to de-couple USD from debt AND allow retirement of the debt. To that end:
If the Social Security Administration were to turn in a few of their bonds to the Treasury, the Treasury could issue them a "Federal Credit Receipt" (FCR). That FCR represents an obligation on the part of the Treasury/Federal Government and is an asset owned by SSA, in the custody of the Treasury.
What that does, is allows the Treasury, Federal Reserve, and potentially Congress to set terms on the redemption of the FCR.
For example, the Federal Reserve economists might determine that a Texas Stock Market is beneficial to Texas in distribution of capital and its economy. So, the FCR might be redeemed for ownership in a Texas Stock Market. The FCR would then be off the books of Federal obligations and SSA would hold beneficial ownership in an income-producing asset.
This plan shores up Social Security, while allowing a way out of the debt, and provides resources to economic development and infrastructure throughout the United States.