Re: BuddyPress and wpMU, some expert advice needed
Re #3 – Your blogs will stay intact. Buddypress will create a few components called groups and forums (if you have bbPress installed). Groups can be configured by users or admins. BP forums are a part of groups.
Re #5 – There’s a few forum threads about integration and a couple of guides floating around the net.
The next version of Buddypress is scheduled to be released next week (August 11), but I won’t be surprised if they push it back a few weeks since there’s a lot of new stuff being implemented.
Right now, if you want a tight integration, you’ll have to theme WPMU and BuddyPress at the very least. There’s no way around it.
Groupblog plugin – https://buddypress.org/forums/topic/new-groupblog-plugin#post-19344
– It’s still in development… I would just test this for now
Community Blogs for BuddyPress – https://wordpress.org/extend/plugins/bp-community-blogs/
– A revision was made by Boone Gorges available here – hxxp://dev.commons.gc.cuny.edu/files/2009/07/bp-community-blogs.zip (change hxxp to http)
– I’ve been meaning to test this, but haven’t yet
Keep in mind that these plugins would give a group a blog, but not a forum for each blog like you want… both have a different way of achieving this method.
The groupblog plugin would be more tightly integrated, whereas the “Community Blogs” plugin provisions group members to an existing WPMU blog.