Halo 3 and Halo 2 had a party matchmaking system. If you searched alone you got matched with other people searched alone. If you searched in a full party clan you got matched against a full clan. You can't have a strict matchmaking system if they don't correct that problem. Clans would just destroy randoms.
Overall I don't like the idea of a skill based matchmaking system. It's only going to shrink the community further because cod has a large casual audience that includes 30+ year old gamers who don't really have any time for that because they just want to hop down and play after work. Halo made sense competitive, but just let MLG and esports figure out the competitive stuff. We don't need it in a game where connection is a constant problem hindering true skill.