let the companions have 5 slots for different costumes like our main toon has.

At the low, low price of 1200 CC each. 🙂

I would rather they just add a wardrobe feature, that allows the saving of your max number of outfits, and they can be applied to companions as well. Granted, that eats up some space if you want each companion to have their own look, but when you want to change it, you would only need to save over the outfit slot, but without having to pull all of the items from your collection, bags, or cargo. Put it all in a design UI, along with a Weapon designer, that can then be applied at any time to your character or companions.