I don't realy understand you, but you can cheat weapons. I made a hack that can switch ingame to a other weapon. You need to override your weapon with the one you want. This is posable with a simple memory copy. You don't get the weapon for real, but you can use the weapon with the stats in game.
If you only copy the weapon then the skin will be the same, if you drop the weapon then you see the skin of the weapon you cheat. If the hack is only for your self, copy the weapon that you want to the weapon that you have. Restore the old weapon's back on crossfire close the avoid crossfire errors.
Warning, you are the only one who can use the stats of the cheated weapon. If you cheat in the lobby to the weapon you want, then you will see ingame the weapon skin of the chaeted weapon. This will work perect, don't cheat a weapon like a M16 to a awm, the awm has to mutch bullet damage.
In some modes this works, then you get 12 bullets in your awm

. If you cheat a m700 to a m16, then you can shoot all the bullets in 1 seconds... But the bullet damage will be low.
But why you don't make your own custom weapon with custom stats? That is mutch beather.