What if premium cards will have a counter of how many of them exist in the game? Maybe not for all of them since premium commons still be very... well, common. But some combinations are very rare or, after some point, could be even unique (end of preorders, sets rotation, limited sets of cards with an alternative art and so on). I think for traders and especially for collectors could be quite interesting and usefull to see, that in the whole game exist only 5 copies of a card (and there never will be more for various reasons).
It also will help to determine price of a card on the market for those players who aren't pay much attention to trade channel but who were lucky enough to get something like gold-foil Zomborg in a draft/booster. Especially if in the game will be an auction house with possibility to trade cards for IP\LP and\or secondary market with trading for the real money.
I suppose it could be not easiest feature to do, since it could demand a lot of calculations for the server but maybe in the future... Or these calculations could be made not in the real time but once in an hour or a day.
At last, feature like that could be implemented only in a digital game which is one of the selling point of the Infinity Wars