The impression I get is allowing them to be purchased at all is grounds for the payment processor to suspend their account. So this solution is a no-go.

Probably the only way around it is to spin up a completely different corporate entity which only allows for payments via wire transfer, ACH, or perhaps some of the various payment apps available.

FWIW https://www.federalreserve.gov/paymentsystems/fednow_about.h...

Like I said, that smell like anti-competitive behavior. It basically means the payment processor denies competitors a business opportunity for cases they don't want to service.