I'd just like to see "chasing x weapon" being one of the core gameplay mechanics to "chase x item that let's you swap one perk". Mods arent that big of a deal. Perks are. Say you have Grave Robber and Multi Killclip, but you want Feeding Frenzy instead of Grave Robber (if it's in that weapons pool). So you use Glass Needles like item to reroll GR. That slot is now locked so it is the only one you can ever change. Maybe you dont get Feeding Frenzy, but you can grind out another consumable and try again. Maybe you got a god roll auto rifle but it has 2 long zoom scopes, reroll one scope until it's short or medium. Or, Bungie could do new mods and a perk swap system.