Yea, I've got 5 or 6 friends that all play, and it'd be really cool to do the Session challenges together. Especially if the requirements were increased for more players.
I could see Line challenges being kind of annoying to play with more than 4 people though. There's already usually 1 or 2 people we have to wait on who are struggling to finish the line and that would only be worse with more people.
Throwdowns already support up to 10 players though, so at least there's that, it's just annoying that the only joining options are "everyone" and "party". If they're not going to give us larger parties, there should be a "friends only" option, so we don't all have to jump in the throwdown before some rando does.