It's very hard to get regulatory approval for a banking charter right now. The FDIC has been approving less than 1 new bank a year since 2009, as compared to an average of 154 a year in the eight years prior to 2009[1]. And that's just one of several regulatory bodies that would need to approve a crypto bank.

[1] https://www.bankdirector.com/index.php/magazine/archives/2nd...