phpfox customization - public lists

I want this customization for phpfox: Admin can create "Lists" and add users to them, and also any user can join any list, and when posting anything, the user can decide on each post which lists he wants to share the post with. Lists are public, that means anyone can see all the lists, the users registered to them, and join or leave any of them. phpfox v3 is the version to be used, since it already has custom sharing options. Dehed.