Did anyone think at this? How would a bank work? How could you loan bitcoins and get interest for them in an economy with just 21 milion BTC limit?
Ripple do have some resembling feature as you stated here. But the question is IF such bank is formed....Who will be Administrating/manage this bank? Being decentralized nobody can control or regulate BTC transactions, So if there is no control there is to guarantee of re[payment of loans.
It seems to me that if Bitcoin Bank is created, each user will hold very strong control and this will completely affect all the advantages of the crypto currency. To date, the authorities and governments of countries in which Bitcoin is legalized can act in the same way, or they are already acting in this direction. But how will one bank differ from the existing banking system.