Hey Mark,
I see it from the same angle like you!
Splitting up the "crowd" into topics will change the motivation to engage and post.
I also started a community "video" (https://beta.steemit.com/trending/hive-178335), i am not sure if the topic is to broad but i'll see how it will develop.
I think a game changer would be a individual coin for every community, to promote posts in example. Do you know if something like that is planned?
p.s. already joined your community :)