In his new post, Jadzi mentions:
"Also, I should note that as it stands now in Beta, the current restrictions on what you can add to the wardrobe are being removed. You'll no longer need to be able to equip a piece to add it. So, for instance, a soloing minstrel could find a piece of heavy armor they like and use it cosmetically."
This means we would be able to use any item - heavy, medium, light of any level and class without need to have a character being able to equip it.
It would be absolutely great for all of us fashion freaks if it stays like this to the live release. My top heavy character is still only level 54 and I was already worried how will I level her up to get access to T7 crafted heavy items, which I hope will be beautiful. Let us pray! :)