Just thinking out loud here, but if the government operated a bank they could apply some common sense to the whole system:

* Allow any legal transaction (so if another payment processor refuses you, you have a backup)

* Allow an account for any legal entity (so no more debanking)

* By setting rates for savings and mortgages, it would provide a soft range for other banks to move within

* The state would only have to guarantee its own bank. If other banks crash and burn it won't take down civilisation