Just an idea, I am not sure if its a good one or bad, but think I would come up with it anyway.
Every week there is one arcane stone that is available in the Reward pack along with an ultra rare/epic troop,some gold and keys.
However what if there was an option for us to buy another arcane than is in the weekly reward pack for gold?
Not sure how much gold it should cost, but surely a little expensive. Then at least we would have the option to get x amount of two differently arcanes a week.