They should keep credits for the armour and everything, but also have a skill level like halo 3, what I mean is, you still rank up like in halo reach but you also have a skill rating to show how good you are at the game, the skill rank would determine who you get matched up with, and the credit rank will simply show how long you've played for. It would have the 1-50 rank next to your name, then it would also have the credit rank next to that.