One thing that I've always wanted to see in Multiplayer is a color-earn system.
My idea is a K/D ratio color earn system. The system would be set up so that your armor detail color is directly proportional to your K/D ration.
I was thinking something like this.
>.8=Pink. Cause, well....you suck.
.81-.9=Baby blue
.91-1=Solid blue or Solid Purple
1-1.1=Solid red or Solid Green
1.11-1.2= Black or grey.
<1.21= Glowing color of choice.
Naturally, the colors don't have to be that. I just think it would be cool to see your opponent from a ways off and know what kind of fight to expect. Is he a punk or a god? This way you could have all kinds of new call out "Glowing at our training" etc. I think it would be pretty cool to have to earn your colors, like armor, through skill rather than having no life and finding all the skulls.
Also, I would love to be able to see a players stats from the last game. You may be a level 25, but if you just went 34 and 2, I'd love to know to pay special attention. If K/D R were on public stats and gamercard, as well as the last games stats? I think it could add a bit to the tactical aspect of gameplay.