The idea would be similar to crysis's system where you press a button and can switch weapon mods. Obviously you would need the weapon mod in your inventory to do this. I ask for this cause I really hate having to carry around 2 or even three of the same gun to switch to depending on the situation, e.g. a night vision rifle for sniping at night, a normal version for day, then a recon for scouting. The mod would ideally mean if I had a night vision, standard and recon scope in my inventory I would only need to carry, one version of the gun and could switch scopes as needed. This obviously wouldn't work for all modifications, Only simple mods like scopes, muzzle attachment and maybe magazine size (though why you would change that I don't know) would be changeable. This would allow a more versatile approach to combat e.g. Upon approaching a raider encampment, I could equip my gun with a recon scope to mark the enemies, making it easier to keep track of them. After this depending on if its night or day, I would equip either a night vision or normal sniper scope and begin picking them off. Then due to negligence I get spotted, thus they all come running at me, due to my long range scope I would have problems fighting in this situation, so I switch out to a reflex scope so I can fight them without the nausea of constantly zooming and unzooming to target them. If I was playing without this mod I would need to carry 3 gun minimum to pull off this situation, which if said guns are gauss rifles that about anywhere between 40-60 extra weight depending on mods. With this mod 1 gun and 3 to 4 different scopes. Mods similar to this: Portable Crafting Tools Roleplaying Elements - Portable Scopes