A few things:
It would be pretty cool to be able to completely holster your gun, like carrying your badlands rifle on your back and your revolver on your belt- it may be a little difficult to implement but it'd look really cool
Also:
What if you can only carry one of each type of gun at once?
Either
A) You can carry 1 pistol, 1 rifle, and 1 smg at once.
B) One large gun- (rifles and larger submachine guns) and one small gun (uzi, smg lost, and pistols)
C) 2 small guns & 1 large gun (pistol or small smg & rifle or large smg)
Grenades and slams can be carried as well, but like a limit of 3-5 nades and 2 or 3 slams.
You can still carry them around in your inventory, but this kind of thing could be used to help increase the RP element due to the fact that it wouldnt be easy to carry around an arsenal of weapons across the wasteland, not to mention that most people won't carry that many weapons at once anyway, I just think that these two ideas: Especially showing your weapon on the player's model
Would be AMAZING
On another note: I was playing css the other day and I would LOVE to see the M4a1 added, or maybe dual pistols if possible