It's been suggested before no doubt but it's worth mentioning again. Tons of lower level/rank sets that cant be used because they are too weak.
So the suggestion is: Allow the use of crafting to upgrade lower level items to higher levels/ranks. For example say I have a vr14 master's weapon that I want to be vr16. I then use materials from the appropriate crafting line to upgrade it. Make it cost a silly amount of materials, as long as its possible.
Some kind of reforging of the item to a higher level.