> one of the problems with replacing credit card companies like VISA are really technical

VISA and Mastercard never resolved major technical problems. It's nothing a bank wouldn't already be able to achieve internally from a technological complexity point of view. They didn't invent any of the technologies, they just navigated the political and regulatory hurdles, then leveraged their position for more.

Your comment makes it look like the problems are "just" political or regulatory. These are more often then not the bigger ones.