Yes I understand his Idea, but Cairne is really important, after clearing the board when N’Zoth summons your minion you will still have 4/5 on board.

Hard to replace it, There is no high mana minion fits for this deck
Best replacement is (FREE FROM AMBER) in my opinion, but you can try one of these cards

KABAL TALONPRIEST
CORPSETAKER
ETERNAL SERVITUDE
SHIFTING SHADE

Good Deck, I think you need to add Cairne, also a minion that destroy weapon plus Doomsayer.