I know it's very easy to suggest it, and god only knows how hard to do, but this would be a HUUUGE QOL improvement.
So instead of leaving to see what your fit looks like, and then redirecting back to where you previously were from scratch every time you go back in, have the skinbox access the ingame inv preview of our char and dispaly it in the skinbox window. Then we can mix and match and see the result in real time. Anyway thats my "impossible to implement cus its an old ass game with funky limitaitons" suggestion