I've seen various arguments for "killing" or "excluding" certain payment methods because of security, cost or other problems (check, CNP). I'd agree that hidden cross-subsidies can be problematic. That said, I tend to prefer the idea of building an IoP Framework where any payment model can connect, initially perhaps at the semantic layer. By providing a more consistent end-user experience or interface (for machine or human users) that would, I'd argue, facilitate those users transitioning to "better" payment methods. That's especially so to the extent the IoP Framework helps to decouple payer and payee side adoption, reducing some of the chicken-and-egg hurdles. Such an IoP Framework, would also, I suspect, heighten the competitive pressures on solution or infrastructure providers that fail to adapt.