If used for classes, the instructor would presumably be the one owning and controlling that group. As the class completed, the students would be removed, and when a new class started, new students could be added in. The membership in the umbrella group would automatically cascade up, without an enormous amount of work.
The umbrella group might have a few blogs, others organized as chats, and yet other groups organized as forums. A group may have one, two or more of these, as could the umbrella group.
This could also be used for classes in various institutions, where each has their own private area, but they have an umbrella group that they can all participate in. An example might be creative writing classes in universities and/or high schools, when the sharing of ideas and commentary might broaden the experience.
I see that this can be done with gforum, (which is currently in beta), but I would like this functionality to extend to chat, (such as rocket_chat) and blogs, such as blog. Ideally, it would be usable for any node type assigned to a group.
Clearbrook → created an issue.