To all the people thinking this wouldn't be possible in Arma 2: Let's consider the example of a scoped Lee Enfield. You could, internally, store two weapons called something like lee_enfield_default and lee_enfield_scoped and then make lee_enfield_scoped have a right-click option of removing the scope. When the user clicks that option, the item lee_enfield_scoped is removed from the inventory, replaced by a new item lee_enfield_default and additionally, the scope is placed in the user's gear. Said scope would have a right-click option "Attach to rifle" (or the more specific option attach to Lee Enfield, if due to realism the scopes would be limited to certain weapons) that would simply remove the scope from the gear and add the lee_enfield_scoped weapon. Why isn't this possible right now? Checking if something is in the inventory (like that you actually have a Lee Enfield when you want to attach a scope), placing items in the inventory is possible and removing them is as well.