I opted for the new wearable item solution (I think the human and body item/gump are hard coded into the client) using the layer number 5 (the shirt's one).
When I wear the item, my paperdoll's gump changes correctly, but there is a way to prevent the user's drag action?
Even if I set the item as Movable = false, players can try to drag away the item and the skin disappears for a second until they see the message "You can not pick that up".
Thank You!