But I think many other
people have thought of that already too.
The 10% discount the credit cards wouldn't have to pay for if it was done like the American Express Open discount network you mentioned. That is a deal they have worked out with the companies so the price they charge Amex for a $100 purchase is only $90 if it's 10% off there.
That way it doesn't cost the credit card companies anything and it's good for the restaurants because it would give us a reason to go there.