That's like, literally impossible? "Hey I just invented ameliuspay, your shop doesn't support it, go directly to jail"
The closest you have is SEPA because it's universal on all Euro bank accounts. And many webshops do offer it. It doesn't integrate into credit card workflows because it's a push payment - you have to go to your banking app, type the details and send the money, while the website waits. Some people might have to go to an actual bank.
If ameliuspay is properly registered with the EU payment processor platform, then it should automatically appear as an option in the webshop.
What does that even mean, and how is that "EU payment processor platform" not a payment processor itself, meaning that you're mandating one specific payment processor?
Hacker News moment. Imagine someone over 60 whose career has nothing to do with computers trying to make sense of a list of 45 different payment processors to choose from.
And if they miss even one of those 45, EU enforcers burn their business to the ground. Oops, now it's 46. No, 47.