well. i don't think EVERY Unique/untradable item should be able to be stored. because like heck you can actually get more then one Unique item. just store in the Retainer. and run the dungeon again and it will let you loot it a second time.
it would be nice to see the amount number show for if you have one in your Retainer(s) or not. it would save a lot of time. so you don't have to constantly compare items.
but i DO think every limited item should be able to be stored. like items in any of the event they hold. all pre-order and CE items. these items are already taking up a page or two. and they gonna keep expanding. eventually there won't be room for stuff of an actual practical use.
i wouldn't even be throwing away half the stuff i do if we had a better armoire. it should obviously allow us to store only one of each kind.