Not a bad idea but needs some tweaks
You'd probably find a vast majority of items would be considered needed because there's a vast quantity of commendations that apply to each loot.
For example, Lets say I'm picking up a Captains Chest
Earn 150,000 Gold with the Gold Hoarders
Sell 360 Captains Chests to the Gold Hoarders
Sell 600 Gold Hoarder Treasure while Gold Hoarders Emissary
Sell 320 Gold Hoarder Treasure While Grade 5 Gold Hoarders Emissary
Sell 480 Gold Hoarder Treasure to the Reapers Bones
Sell 600 of any Treading Company items while Reapers Bones Emissary
Sell 320 of any Trading Company items while Grade 5 Reapers Bones Emissary
All of those are commendations affected by selling a Captains chest and a such would affect the 'needed' or 'not needed' value on a chest. You'd find almost everything you sell in the early to mid game would be considered needed in one way or another.
A better way to implement a Commendations assistant would be to press a certain button while holding a chest and it would bring up a menu showing every possible commendation this chest could affect, this would therefore help you identify what to do with it. Ie if you have a Captains Chest and it says needed, it might only be needed for Reapers and not for Gold Hoarders, so simply saying needed would not help you know what to do with it unless you dig into your commendations page and find out what it is, which eliminates the entire point.