I think you could set up something clever where the QR code redirected to the correct menu 95% of the time, and maybe it didn't charge the credit card initially

I think you could set up something clever where the QR code redirected to the correct menu 95% of the time, and maybe it didn't charge the credit card initially, and that would last longer than if you had charged something immediately 100% of the time. However, I think your point still stands that it's not worth the trouble and it doesn't scale well.