Okay so this would be simple and only sold by Xur. Level 1 Upgrade Device Price: 15 Strange Coins Turns a Common weapon into an Uncommon Weapon. During this shift you can choose to add a perk to your weapon. Afterwards, the remaining points go towards either a Strength, Intellect, or Discipline bonus. This would be balanced out by having stronger perks take more points. Level 2 Upgrade Device Price: 20 Strange Coins Turns an Uncommon weapon into a Rare Weapon. During this shift you can add another bonus to stats and a increase the amount of upgrade options such as scopes or reloaders. (You get to choose) Level 3 Upgrade Device Price: 25 Strange Coins Turns a Rare weapon into a Legendary weapon. During this shift you can add yet another bonus to stats as well as a second perk to your weapon. Level 4 Upgrade Device Price: 30 Strange Coins, 15,000 Glimmer (both, not either or) Turns a Legendary Weapon into an Exotic weapon. During this shift you can add a final perk to your weapon. This perk can be unique or standard. You also get a final stat increase and the ability to modify the design to an extent. (you might want to crack or uncrack the scope of the Khvostov for example.)