Seriously.. Let us trade and sell cards. There is no good argument against it.

Despite currently having over 350 cards, my main deck hasn't changed since HW. It contains easy to acquire cards and the only thing that's likely to change it at this point is the addition of another 5 or 4 star card allowance.

The genuinely difficult to acquire cards will never be played because they're all junk. They're collectibles, nothing more, yet they can't even be shown off. It would make no difference to the game balance at all. Even if it did there still wouldn't be a good argument against it. We can buy and sell minions and there's a competitive game that uses them as game pieces.