BuddyPress.org

Ok here’s an idea..

1: Install the groupblog component

2: Make the default theme for the groupblog the P2 Theme: http://p2theme.com/

3: Only let the admins add new posts (this can be videos like you said) and the members of the group reply

4: Adjust the p2 theme to your taste so that it looks just like your site

You now have a “wall” where admins can post videos/news/photos which does more then a standard wire does and it’s also fully integrated with groups/activity stream.

It does’nt do everything you want but it could work