NFC add-on

[mitcoes]

Unless you can get the banks on board it can't happen. Given their reaction to rooted Android phones I don't see them supporting a phone where the user can rewrite the firmware.

No need to get the banks on board.

Just one - debit and credit card compatible payment method - as PayPal
that would see the enormous advantage of having the cheaper watch NFC for payment
at their service.

And for security measures, they can help funding new ones.