I don't think Wero can "win" this from just the merchants side. It's got to be better for the customer's side.
So when I from Slovakia want to buy something in a French eshop, I'm out of luck. And when on a vacation, can't use this system either, while a French person on a vacation in Slovakia can't use it either. My guess is people will mostly continue to use credit/debit cards.
I agree this could be a difficult battle and we effectively need some alternative to existing card issuers if they are to be displaced.
Current contactless payments are easy, secure and allow disputes etc.
Why would you think that contactless payment would require Visa or Mastercard?