What They should do I make it so if you have a raid weapon or armor from the current raid it would allow you to upgrade any legendary raid or non-raid to the same Light/Attack as the weapon or armor piece you use for the upgrade. You could use a vendor to to this I think, Vanguard or Gunsmith. To keep it fair you would only be able to use a a helmet for a helmet and a hand cannon for a hand cannon. Say I want to upgrade my Fatebringer, this means I would need to get The Word of Crota (Preferably a second one) bring that and the Fatebringer to the gunsmith and basically upgrade The fatebringer with the word of Crota. Same would work with something like the devil you know. This would allow later down the line to upgrade any of the weapons to the stats of the current dlc, just by acquiring another weapons of the same type. And yes it would consume the weapon you used for the upgrade. The other option is dismantling it and acquiring an upgrade materiel say "Essence of a Handcannon" Then in the description is can say what raid it was acquired from as wel as what stats it will give the weapon you upgrade. This would also fix the issue of most level 32s looking exactly the same..