Made an account just to reply to this topic. The ranking system for Halo 4 needs to incorporate all the best features of the past 3 games. First of all, competitive 1-50 ranks need to come back, similar to Halo 2. Trueskill should not be used at all, for anything. Halo 2 had a great competitive ranking system, easy to rank up at first, then progressively harder. If you lose too much, your rank goes down, if you win enough, your rank goes up. Very simple yet quite effective. Showing a progress bar, like Halo 2, would be a great way to visualize how many games are needed to go up(or down). THIS KEEP PEOPLE PLAYING YOUR GAME, HENCE BETTER SALES FOR MAP PACKS!
Social/unranked games could just be done like Reach. Have a hidden skill rank for to get fair matches(assuming reach does this, I don't know) and visually show a rank that goes up but not down. The more you play, the higher your rank, be it Military or Numerical or whatever. To make this more popular, you could call the playlist something other than unranked/social. Call it linear or whatever, I don't know, but the small % of Halo players that want a ranking system like COD can get their fix here.
Bottom line is that H4 NEEDS ranks 1-50, where losing too many matches can make you lose your level.