It so happens I designed a scheme a lot like this: clients send an opaque payload which the service provider wraps and forwards to an authenticator. The authenticator simply replies with a yes/no statement of whether the user is a legitimate participant in the scheme. The payloads are compared offline to validate that the versions of events given by the user and service provider are the same. There's a lot more needed to make it trustworthy, though.

It took me most of 5 years to obtain a patent on it: https://patents.google.com/patent/US9853964B2

To me the primary advantage would be to open up an untapped segment. There are readers who will never pay, they see ads. There are readers who love a source so much they will pull out their credit card and deal with the hassle of having yet another subscription. In the middle is a large, untapped group who would pay if the transaction costs (pulling out the card, hassle of multiple subscriptions, worrying about how much they're spending etc) were approximately nil.