Pretty much what the title says. I'm assuming armor classes (Light/medium/heavy) were initially designed to be relevant to each class but let's be honest, the designs are all over the place at this point with heavy having cloth-looking armor and vice versa. The only relevance with armor classes is mostly stats at this point. It would be amazing if Anet just finally made it so you could transmute all acquired light/medium/heavy armor in your wardrobe for any class. It would take "Fashion Wars 2" to the next level with far fewer compromises to be made when outfitting your character.
You would still need to acquire each armor with the appropriate class of course but once you acquire it you can use any class to have that appearance. I can understand some exceptions but it would be awesome if we had a bit more freedom. Probably won't happen but one can dream.