i think a true skill ranking system is needed for halo 4. there is no benefit from winning in reach but too much cheating in halo 3.
i suggest a ranking system 1-50, 5 wins in a row to go up 5 loses in a row to go down. this way boosters quitters and restarters dont benefit. ppl with high xp go up the same as low xp ppl. bad teammates would only cost you your win streak and not your rank unless u already had a 4 lose streaks. this would also slow the time speed of getting a 50