So as I already wrote, 15 years from now it may not be possible to buy something using Bitcoin without trusting some CA, which are controlled by government.
This just isn't how it works. You keep repeating this, but it's nonsensical.
You can transmit a payment request via whatever channel
you want. If the x.509 non-repudiation signature in it is not secure
you're still secured by whatever channel
you're transmitting the data over. If
you have no secure channel at all,
your problem is ... kinda out of scope for the payment requests.