Some good points, some odd ones (why would you really need a hierarchy of groups inside of other groups?), but the interface part is mostly wrong/exists already.
I just looked at it and I can't find an interface to re-organize my current list of friends in Lists.
Account->Edit Friends, each friend has "Edit Lists" next to them on hover
I also can't find a way to filter the messages only from people in a certain list
Click the arrow beside Most Recent on the News Feed, then you can filter by any list
Lists also have the same problem as groups, they are categories for people, meaning that one person can only belong in one List
One person can belong in as many lists as you want them to
And when posting a message on your wall, is there even an option for posting only to a certain list, as I can't see it.
Click the lock beside the share button -> Custom edit -> Specific People -> Type whatever lists you want