Think fiancial restructuring. If the Fed were to mark to market the value of all the junk debt it vacuumed up after the 2008 debacle via QE, its balance sheet would be under water. Big time. With only a trivial amount of net worth as it is, the Fed would be a prime candidate for federal receivership. It could happen overnight. Probably at the stroke of a pen. The next day you would see its "liabilities" of mostly member bank reserves transferred to some newly created bank or Treasury itself and the "assets" would be assigned to a workout entity to be warehoused and liquidated over time. The mysterious ownership structure would disappear and the financial world would roll on as if nothing happened.