Notionally, opening new banks and/or buying an existing one that lacks current customers is feasible. Presumably once you do that, you could easily plug into FedWire/FedACH/FedNow, which would allow you to process electronic payments on behalf of whomever you choose to bank, as long as you comply with all the KYC/AML and other finance regs. You might not be able to process visa and mastercard, but virtually any of your customers' customers presumably still have financial accounts that are enabled on Fed rails, which will not be as likely to discriminate. Requiring end-customers to initiate payment (push) as opposed to doing pull, would also reduce transaction reversal risk.

I don't really the ultimate purpose of the position taken by either side here, but it does seem to me that there's a path by which both can coexist, even if difficult.