Hearthpwn

I like the idea of bolstering the achievement system.  I proposed something similar to Noxious' system after Naxx came out and was lacking flare.   It would be cool if there were meta achievements similar to WoW and or regular achievements even that could be achieved by killing bosses in a special manner.  This would also make some of the encounters much more interesting.  

Kill Instuctor Raz with a mind controlled minion

Last 12 turns vs. Patchwerk

Kill Noth the plague bringer without raising a single skeleton.

There are so many possibilities and they would also be able to encorporate much more game flare that were parts of the raid encounters from WoW.   They would require crafting special decks to achieve the special goal, and in most cases would probably be much more "fun" than the RNG requirments of simpliy killing the bosses on heroic.   I would add as a reward to these meta achievement "guild up tokens" similar to Noxious' that could upgrade Naxx/BRM cards to their golden counterparts.  A complete Naxx golden set cost some 32,000 dust which is just silly.