What banks "can offer" is irrelevant until they offer it in practice.
As a customer, I have zero interest in paying for my lunch via "QR codes, email addresses, and mobile numbers" when I can do it with near-zero friction with a double-click on a phone (funded by a credit card), or with a tap or swipe of the credit card. I also have better protections. Switching costs are non-zero and I will only switch if there are some substantial benefits; pure "feature parity" is a reason to not switch.
The benefits to merchants are tangential to me, but there is a substantial downside of all the merchants having to do integration with an additional system.