since leather jacket is the lightest armor (2267grams), it's the best one for a mule/crafter if you get a high +carryweight bonus with crafting.
leather jacket looks too badass for a crafter guy, robe suits this purpose more.
I suggest making robe lighter so it would be better for such function, it's currently 4535 grams, so maybe make it around 1500 grams? defensive stats could be lowered or/and crafting requirements higher to make it fair.
I realize this might seem unimportant to many of you but it would make a nice detail and will probably take very short time to change, so why not?