It is an issue. You can't remove the armor from one companion and give it to another. You have to keep an armor set in your inventory or go buy a set for the sole purpose of getting a set you want off a companion.
I'd like to remove armor from a companion and use it for another. As it is, I have to replace their armor with other armor that I keep in my inventory for this sole purpose. It would be easier to just be able to unequip and have them revert to their default look.