The thing is, forget about the armorie as extra storage space because it's not. The armorie does not work in the same way your inventory or retainer works, it works by actually physically deleting the item completely from your inventory, while flagging it to be restored when you want to 'retrieve' it (this is why it resets all customization made to it like dye or spiritbonding when you retrieve it, the original version is deleted and it's simply restoring it to a default state as it is essentially giving you an entirely new version of that item).

Hence why they're deliberately careful with what items that they allow to be placed in it - the more items they add the greater the chance of a bug getting into it that could cause issues to the whole thing - can you imagine the outcry if for instance someone was able to store a fully melded and completed anima weapon in there and due to a bug it ended up being lost forever?

SE are actually being wise in this regard by being very careful about what items they allow to be placed in the armorie for this reason.