The biggest differences that jars discussion on manga as opposed to anime is that 1) everyone reads at a different pace (while an anime ep automatically takes up 20 min of everyone's life), and 2) weekly outputs of manga is a bit more fickle than weekly outputs of anime.

If there's a way to regulate manga discussion like, "discuss up to chapter *** here!" and change that weekly or something, especially for existing mangas that have a lot of chapters that newbies need to go through, then maybe it's plausible. Sounds like a kind of book club to me so it'll take everyone who's participating to agree. I don't know about you guys, but if we had something like that, I would probably restrain myself and not rip through hundreds of chapters in mere days just for the sake of a bit of discussion and speculation.