That make a lot of sense: a /c/hobbies makes more sense than making 200 communities for each and every hobby you can think of.
And really it'd just be a case of making sure it gets mentioned and surfaced to people and that the server and mod teams are up to the task of dealing with broad topics and just keeping things civil rather than trying to police content.
I thought about doing a community similar to that for some things but then realized I'm not entirely sure I want to be the "owner" of something that might end up with a lot of traffic and so uh, haven't.