Why not limit black pendant?? Semi limit black pendant, and the deck becomes way less reliable. If it needs more, semi limit either golden bamboo or cursed bamboo. It wouldn't take much to make the deck more balanced, yet leave the cards still useful for draw in other decks.
i dont think they will ever limit UR cards from boxes, because some people could have spent alot of money to get 3 copies. however, i think they can limit N/R cards from boxes as they are easier to get...