With current Xbox live friends system, when you accept a friend request you put this person into a pool of different people. To find this person you have to scroll down pass all your friends until you find the specific one. However, why not have a sectioning system?
say you have a group of IRL friends who know who you are. well you would make a section called 'irl friends' and only selected people can go in that section. another example could be if you are in control of a clan. to keep your clan separate from your other friend you can create a section called 'the clan' or whatever you want and then put your clan in to that section. Even further, if you need to send a message to that group of people you can select the section and send a message through that method.
tell me is this a good idea? i don't really know, but it seems pretty good to me.