What I don't want to see is a year after release having most players on the server on the top ranks like in COD4. IMHO they should do something about it by:
1) Having a controlled general stats system like BFBC2, but restricting each rank to a certain percentage of the community, so we wouldn't have everyone in the same ranks nor advancing together toward the upper ones. For instance to achieve a certain rank, you wouldn't only have to earn a static minimal amount of XP points, but you'd have to get more points than other players, like in MMORPGs.
2) Applying the same procedure of the hero system, that has been claimed to be server based, without exceeding one hero per team. But the server based rank system would be basically the same thing as the first option I suggest, but based on a percentage of the players in the servers. Say there are 10 players in the German team, but only 4 of them would be sargeants.
But if the rank system turns to be something just aesthetic, it shouldn't get that much attention and neither of these options would be necessary IMO.