Maybe your idea is good to develop a crypto bank, but that's just for you, if I'm not mistaken crypto has been developing -+ 15 years, I'm very sure someone has done that kind of idea, but I don't see them succeeding in doing it.

Developing a crypto bank is not the same as developing a traditional or fiat bank, where fiat is supported by many groups and people trust fiat banks more than crypto banks, that is a fact that happens in the field.
Before you develop a crypto bank, of course you must have special support for it, such as: national and international government approval, support from the wider community in general and you must be able to physically show digital currency to customers to be able to operate your bank, are you able to do these points, otherwise your efforts will be in vain.

The bank's main feature is security, how do you apply security to customers' crypto assets at your crypto bank, for example hacking and so on, who is responsible if that happens and what if the customer wants to withdraw cash, what do you give.

If your idea is successful, maybe we will see that every country already has a crypto bank, the proof is that it has become a myth.