The chip inside claims to support Bluetooth Low Energy, Bluetooth mesh, NFC, Thread and Zigbee. Maybe someone can hack together a payments app using the NFC?
Payment is more of tamper resistance and trust problem than protocol problem. You don't want a hackable card tied to your credit.
Speak for yourself, I'd love one!
Banks probably don't want it, though.
You can't really, unless you get involved in the financial systems afaik. It's not just some open thing that anybody can implement; there's a chain of trust involved and for good reason.
Maybe you could reverse-engineer HCE from bank Android app, but that would be rather fragile.