They could swap it for a different perk easy enough. At one point you could have rangefinder and shot package on a shotgun in the same roll. Was patched 10/14/2014, both perks were then moved to slot 3, anyone that had both logged in to see one perk changed to grenadier, (think it was rangefinder used to be in slot 1). They could easily switch it out for luck in the chamber. Would only require a hotfix i'd imagine, the same method they used with shotguns.