I was thinking like this: you can only overwrite scopes on scope slots, barrels on barrel slots, and abilities on ability slots, with damage / armour slots un able to alter. so rare stuff would only have 1 slot, legendries would have 2 (with multiple choices where they appear). This way we don't worry about gear getting op with all new upgrades, but it becomes more a way of customising armour to suit your playstyle. I would say not to have multiples of the same slot on an item. You could put max hand cannon ammo on 4 armour pieces, but not more than 1 piece.