Love it! I'd like to emphasize the 'Few layers' because if you go into too much details you end up with god awful pictures like player emblems (i actually have a cannabis bud as my own atm) I've always wanted my secondary to have a skin aswell as my primary and maybe not the same style.
Same again with the face camo you'll be seeing army men with cocks on their forehead, which is cool with me, gives me something to aim for.
different knives would be class! maybe even multiple throwing knives you can wield. im not saying more than one unless you have some sort of setup like warlord and tomahawks.
Mask perk slot sounds brilliant it'll take some perks from the orignal 3 perks but and add it to your head which means overall more variation and more perks entirely, which is always good, it adds complexity to the create a class.
all these cool perks we get like scrambler, hacker/sit-rep, eavesdrop, reconnaissance, ninja(mw2)/ninja pro(bops) and tactical mask. never mind the new ones IW could come up with like something little as any killstreak that involves leaving your player vunerable to enemy players, you can have a picture in picture like a camera spike does, which may take up a perk slot but will make your killstreaks even longer.
we want to be unique fighters for online gameplay just like any other game we want identities and to prove we've got skill so may it be you receive something for completing an achievement or because you've maxed out your prestiges we want customization on a next level scale.
This is just a quick response to your post before i go to sleep and i may add more ideas of my own about customization.
TL;DR We're all unique and want identies that we create ourselves so please IW, MORE CUSTOMIZATION !!!