I don't use a wardrobe, because it's just plain inadequate. I, and I'm guessing everyone else, do not want to swap out my merchant robe, or my rings, when I'm switching outfits. So, new interface:
Add "detailed..." button under all three wardrobe slots.
When in detailed mode, you have a list of all equipment slots, with icons of items that are at those slots in the wardrobe (can use crafting icons) and checkboxes next to them.
Under that, a "switch equipment" button. When you click it, all equipment in checked slots will be swapped with what you're currently wearing.
Next to the "switch" button, "check all" and "uncheck all" buttons.
You can still just click on the slots without going to "detailed" to swap everything.
That is all.