I think it would work like how it does here, where you can access/edit all the pages on independent wikis hosted on different servers with one account identity. Federation is about getting both the advantages of centralized services and independent operations (sometimes disadvantages too), and I think outside of forums, fan wikis are probably the best sites for a federation structure. After all, wikia/fandom already kinda operates like this.
I think it would work like how it does here, where you can access/edit all the pages on independent wikis hosted on different servers with one account identity. Federation is about getting both the advantages of centralized services and independent operations (sometimes disadvantages too), and I think outside of forums, fan wikis are probably the best sites for a federation structure. After all, wikia/fandom already kinda operates like this.