This script adds the item LayerChangeDeed that allows a player to target a BaseClothing in his/her pack and change the equip layer to any valid layer that they choose.
To add the deed, use "[add layerchangedeed" for a deed that has only one use. Use "[add layerchangedeed 50" to add a deed that has 50 uses. Use "[add layerchangedeed true" for a deed that has unlimited uses.
I've seen several posts in the past looking for this kind of thing. I threw this together mostly as an example as you may not want to limit your targets to only clothing. Also, I probably included too many layers (or not enough) to choose from but you can edit which layers are valid at line 22 where the variable "Layer lays" is defined.