I'd be happy with just a facial customization, nothing more. Pick your skin tone, and other facial details, such as head formation and facial hair. Or you could use the Vision camera, or later on, the Natal.
That and maybe being able to chose what you wear on your head and face. It would be cool to be able to put on a beret, and chose the color. That is as far as I would go for color choice so we don't have power rangers walking around.
It amazes me that despite the amount of big fans on this site, plenty of them still have no f*cking clue what kind of military force you play in this.
Given that force's stature, probably be okay now to have them customizable, though I get the feeling though that, if they still care about knowing which class is who, equipment won't be unless gamers can handle 5 or more customizable characters (faction and environment) and each class's own kind of armor and packets and what not which leads about 5 or more attributes to a character of each faction/area which then leads to more customizations then Vegas could get a taste of. If majority of gamers can handle that level of customization, I have no problem though I'm afraid IW might get afraid of the masses unable to do something about this which then they'll just limit the actual customization.