A truly open payment protocol should handle any currency (not force you to adopt crypto coins) and would leave it to the merchant and buyer to agree on their settlement method or intermediary, the cancelation and dispute policy etc.
It's entirely possible then that some options would be available, for example in SEPA, that offer instant and irreversible settlement at zero cost.
It's entirely possible then that some options would be available, for example in SEPA, that offer instant and irreversible settlement at zero cost.