The issue I find with the banks being the sole provider and processor of these Bitcoin certificates is that you could hold certificates denominated in just one face value. And one will need a lot of these papers in their wallet if they want to transact different amounts when buying stuff or services. Do you think this paper Bitcoin certification system would work for buying everyday items like a coffee and a sandwich at lunch or movie tickets or a bottle of water? Maybe parking tickets? Isn't it more convenient to grab a metal fiat coin and pay with that and be on your way?