Some ideas densely packed in! I'm having a re-read to understand. Having an "In Character" meter go from out of character to a canon event sounds cool, and evocative, and usable!
I was trying to picture myself as the GM and how I would create an overall scenario that would kick things off and keep all the different player characters invested in each other. Making the Author a bit more of a shared enemy to defeat (you allude to this a bit in the short version and where to end), and/or having some tables to roll on as a GM to help suggest my meta-fanfic starting point would be welcome.