It's a thought - but I'm not convinced on scale. The market needs to be liquid enough to convert btc into target currencies easily. Otherwise, banks basically get btc, convert to domestic (regulated / 'insured') currency at point of receipt and then you're back in old world payments. N.b. I am straying from my area of knowledge but I am confused as to what would stop a btc based bank going bust or suffering from the same currency controls Cyprus put in place if you have put it in a wallet somewhere (we used to call this a deposit!).