So my main problem with the way ranks were handled in Reach was not being able to accurately assess how good my opponents/teammates are while in the lobby (without navigating through 5 sub-menus.) Reach had the playercard when you highlight someone's gamertag, and that had so much potential. However, Bungie decided to clog up that prime real-estate with Armory Completion, Commendation Progress, and Daily and Weekly Challenges. Who the fuck cares.
When I see someone in the lobby, I don't give a shit how much armor he has. Why not fill that space with more pertinent information, like Competitive K/D or W/L or previous season arena rank. Take it one step further and display those stats specific to the playlist you're in. For example, if you're in the MLG playlist, the playercard would show MLG K/D and W/L.
So no matter what direction Halo 4 goes in with respect to ranks, just please keep this in mind. When scoping out the players in the lobby, the most easily accessible and pertinent information should be the indications of player skill. If I want to find out how many challenges a dude has completed, I'll be fine going through a few sub-menus first.