Remove armor type restriction for transmogs. “Class identity” went out of the window as soon as you added troll pajamas and other goofy transmogs in-game and in the store.
Let people transmog their weapons : 1h to 2h and vice versa. Legion artefacts showed that the weapon you have equiped isn’t a barrier to what you can use visually.
More freedom = more customization = happier customer base. You might even attract new players who love very customizable characters.
That will be all from me.