Currently character has 5 possible body sizes. I would say that clothing should reflect this and have also a size. Larger items should weight more and cost more, while smaller items should be lighter and cheaper. You can wear clothing of different size but there would be penalty to your actions and/or its effectivness depending on size difference.
This would help smaller characters with their limited carry weight, while it would somewhat reduce supremacy of 120+kg Kaumos.