>1. SAAS Freemium: It's free to write on Medium, but if you want a real domain and a few more features pay $10/mo
I think this is a fantastic idea. It has worked on many other platforms such as shared hosting before.
>2. Patreon-ish: Direct monthly sponsorship (subscription) to individual authors
This is also a great model because it allows readers to pay for content that they consider worth while. It has the capability to increase overall content quality, become a platform for new writers, and medium could scrape some small amount of dough off the top for the service they are providing.
>3. Fractional Payment: Overall subscription to Medium as a service payed by readers. Authors are paid according to a formula for how many people viewed their content each month.
I don't think this is a great idea to be honest. This is essentially how click farms already work and has lead to the uprise in clickbait. I see this as the primary reason why sites like Buzzfeed exist.