I had a startup that tried something like this.

Initially we went with a similar membership concept, except people subscribed to one writer directly, and got access to the collective. It barely worked, and we moved over to more of a crowdfunding model which was about 100x more effective.

In the end we worked with major publications and hundreds of journalists, had a million dollar matching fund program, and paid out millions of dollars to writers directly, but it still didn't work as a big business.

This makes me think Medium is pretty clueless about what they are getting into - especially after raising more than $100 million.