Yeah... I'm wondering though, Fossil is based on SQLite - a database - and databases are designed to solve the issues arising when multiple users try to change the same data. (Also, fossil by default works in "autosync" mode.) So it should be "easy(er)" to make a real-time collaboration tool based on Fossil ?

P.S.: By researching this, I've stumbled on a (barebones) alternative to Google Docs : HackMD/CodiMD/HedgeDoc : https://demo.hedgedoc.org/