By definition, if you don't do what VISA is doing, the regulatory state will declare you an illegal payment processor.

Like it or not, part of the baggage of doing that service is being an extension of the long arm of the law.

So "rolling your own" minus the regulatory baggage you don't like, isn't per se "making your own payment processor", but something else.

Bit of a Catch-22, but how it works. Everyone just tends to leave the quiet part unsaid.