I'm in, we actually talked about the same idea a while ago (https://discuss.flarum.org/d/28311-can-you-add-a-function-similar-to-facebook-group/13), I've been thinking a lot of ideas about this since then, even making some prototypes of what it should look like, but I haven't had time to define a definitive list of requirements yet.
@ctml liked the idea too, but as it's been a while so I don't know if he still shares the enthusiasm for this.