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.
Loans are moving the economy for sure and banks keep on failing even with a central bank being established.