Would you like to see banks in cities in the next ES? You could use them to take out loans and store money (which would collect interest over time). I feel like, if the game is set in Hammerfell, it would fit quite well with the mercantilic culture of that region. Loans would need to be paid back (with interest) on a certain date, failure to do so would be a new crime subject to fine or imprisonment (you would get loan slips to help avoid forgetting). How large a loan you could take out would be dependent on your collective wealth (stored in the bank and on your person), there would also be a loan limit (like 50000 gold, or something).

The bank itself (name pending) would also potentially be a minor faction you could join, with some sort of quest system. Maybe something like transferring wagons of gold between cities, protecting as needs be (or hiring bodyguards to do that, for serious RP'ers). Also some kind of acquisition quest system involving persuading merchants and people to sell their businesses and homes to you through speech. Finally debt collection, where you collect debts from defaulters, through any means necessary, and if they can't pay either inform the guards to let them deal with it or enforce your own brand of justice.