Being overly focused on the "lit fic" genre they've overlooked the Wild Cards series, one of George RR Martin's projects.
https://en.wikipedia.org/wiki/Wild_Cards
25+ books, a pending TV show. Most books being mosaic novels with individual chapters written by specific writers, some standalone novels.
Disclosure I've been a publisher of works in this series, but the glue that has kept this project together is their contract. If an author kills or damages a character they give up their share of revenue which stops people from painting characters into impossible corners.