I'm sure a lot of people will agree one of the most irritating things about the game is having to farm upgrade materials for alternate characters... When you have 500 sitting doing nothing on your main.
Personally I would like to see a vendor in the tower that will exchange hadronic essence for sapphire wire or plasteel plating, or whichever is needed by the player. Even if I had to spend glimmer each time I wouldn't mind. Perhaps you would have to reach a specific rank with the vanguard to do this?
Definitely needs to be done!
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You should have been moving your armor Engrams to your Vault for your alt(s) before you got to 1000 mats. That's your bad. I bet you still continue to decode armor with your main character.