Why would people accept paper BTC? People accepted paper gold because they didn't want to lug around gold bars. Bitcoin has a weight of zero and is even easier to hide than paper bills.
He can only be a central bank if he uses his BTC to pay off government officials to get him special privileges. In a Bitcoin world, there is no central government, or only very weak ones.
Loans baby. We love loans.
Private banks didn't have a central bank in the 1800s. That came later as the private banks were often failing and taking the USA into depressions too often. Rollercoaster.