They would still have to have a limited equip cap or there would be little to no incentive to acquire new gear and said players would complain there's nothing to do. Also, the achievements couldn't be challenging at all or it would be years of "Bli$$ hates us" threads on MMOC. They would have to be continually retuned to be nice but not equal or stronger than current gear or it would be considered "welfare leggos." They could not in any way be good enough to compete in heroic+ raiding or M+ dungeons or everyone would jump on the bandwagon that they're "required" and Blizzard is "forcing all players" to have to do all these achievements so that "they could be lazy and not worry about developing new content" since it would require mostly old content to acquire expansion to expansion.