I love customizing stuff.
Maybe add these:
Colored Clan Tag - Prestige _
Colored Clan Tag On Gun - Certain amount of kills with a clan tag on your gun or prestige a gun for a 3rd time.
More Camos - People seemed to really love my Lego Camo idea.
This might be the one I want the most:
Camos for equipment - Combat Axes, Grenades, Betties, Claymores, Shoch Charges, etc.
Each gold results in Diamond. You can get mastery for emblem and clan tag.
I've always wanted to kill someone with a gold tomahawk.
Every one of those added featuresd would add to the code the game has to load in each match, there is a limit to what can be loaded at one time in the game becuase of available ram on the console.