What interests me is that it makes sense to start a “bank” that will take care of customers like traditional banks do. Opening an account, buying a crypt, maintaining a computer, etc.?
Crypto exchanges already do that. It is nothing new. If you want to operate a crypto exchange you can do it now. Nobody is stopping you. It is not going to be cheap however. Possibly hundreds of thousands of dollars you will need to get on your feet and it might suck another few hundred k's just so you can stay on you feet. That's because there is a wild competition between the exchanges already.
Why would anybody choose you over Binance, Coinbase, Kucoin and other big exchanges?
You'll have to spend crazy amounts on promotions/ads. I'd say give up.