I would LOVE to unlock new skins for using my favorite weapons!
At the moment there are no unlocks besides clothing. Having unlockable weapon skins based on kills and headshots is honeslty a ton of fun, it gives you a goal to reach and makes you play more.
Being able to use the in game currency for this would also be fine. But it would be nice to have some sort of challenges.
Anything that lets you customize your character/weapons would be a welcome addition.
Anything that gives you something to work towards is also a welcome addition.