If other people are telling you that it's technically impossible and you can't even come up with a sketch of a technical design that works, that is a clue that

If other people are telling you that it's technically impossible and you can't even come up with a sketch of a technical design that works, that is a clue that it may be technically impossible. No country will intentionally make its economy completely reliant on another country unless things are completely in the shitter (like Zimbabwe switching to US$). Even Visa/MC are a problem in Europe and they only act at the highest layers of the stack - there are plenty of ways to transfer money without relying on Visa/MC but cutting them off would already be a huge disruption.