Isn't this exactly the issue addressed by money laundering? Would this not simply force a large number of people into dealing with organisations or individuals who can convert their existing stockpile of (no longer valuable) cash into a smaller pile of cash that still has buying power? A naive approach would be to 'hire' a large number of people to cash in amounts of notes that would be just under the level considered suspect by promising them a cut of the exchanged money. I'm sure there are existing criminal networks that could achieve such schemes (or better thought out ones) within the window of Nov 10 to Dec 30.