What is your suggestion?: See title
Is this in OSRS?: No idea
Has this suggestion been accepted already?: No
How would this benefit Alora?: Mainly looking at it from the viewpoint of UIMs, it's extremely tedious to carry any armour you don't need, gaining the ability to deposit single items would for example:
Free up this 3rd age hat slot, rather than having to carry it for an eternity to get the full set.
It goes without saying, the other elements of the treasure room would be hugely beneficial as well (cape rack, armour case etc).