Yes, you can clearly see by that title that I had no idea what to call this.
Anyways, my idea is to add another thing to arena that would allow how many rares (cards with two or more slashes) your deck can use, much like how the Upgrade thing works. To cost 20 points, it could either just cost 1 point per three rares, or maybe 4 points per stage, which would go 0 - 4 - 8 - 16 - 32 - 60. Of course, that number can be changed, but this thread is just to show the basics of my simple suggestion.
What it may bring to the game is to encourage newer players to have to think of more creative decks, instead of the shard-spams that seem to flood both of the lower level arenas. Also, it would make one have to more-carefully consider what all they would put in their deck, which may also encourage more unique decks.
All suggestions/feedback are welcome. Feel free to vote in the minipoll.
-n00b