At this point the SMG is no longer an SMG, but is instead more of a light machine gun because of its range. So, why not just replace its skin with something like, say, a US M60. There doesn't have to be any game mechanic changes for now, just a default skin change, with possibly modifying the ammo later on.
Yes I am aware you can change the skins by yourself, but there just isnt something right about it when it isnt vanilla.