I wanted to build this 10 years ago, but I got caught up in the weeds over trying to build a machine learning-adjacent (but before I knew what machine learning was) story engine, that would help ensure internal consistency between branches/merges.
(that is to say, if you fork a story and re-write it so that a major death doesn't happen, it was supposed to keep track of that and remove references to that death later on.)
But yeah, fiction + branching and version control and merging and versioning!
Front load it with public domain content, encourage people to write Female!Holmes, or Queer!Connan, or NotHorriblyRacist!Lovecraft.
Treat fanfiction as an extension of, addition to, and supplement for cannon. Keep track of who wrote which bits, and share revenue from POD books.
@ajroach42 I love this idea, though I have no skills to help bring it into to existence.
https://archiveofourown.org exists, and is great in a lot of ways, but not really what you're proposing here.