Already been done, still waiting on more change announcements before doing too much. Its obvious that stances, like the rest of Warriors, are not final.
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There were a lot of things that happened once upon a time and most were not intended, which is why they are no longer possible.
There was a time where there were light shields in the game, which both hunters and rogues used (lol alpha). There was a time in which we had melee hunters too.
Point is, Arms isn't designed or billed as a Shield DPS, even though they could use shields at one point (as you pointed out) they still weren't a shield DPS class, they were simply using a powerful trick to do better in PvP, something you see quite often actually.