It would depend on how pillar stacks are treated.
If they are treated as a pile of individual permanents, its likely to get something for basically nothing if you load up on pillars, and the opponent has a normal number of pillars and other permanents, but how well this would work would be questionable.
If the stacks counted as one permanent which would give one of the stack, it would seem fair to me. If you loaded up on 2 kinds of pillars and 1 of these, with nothing else, every swap there is a 1 in 3 chance you lose the polar exchange and can't use it anymore.
The second situation sounds more right anyway. It is how pests drain quanta, and gifting 1 piece of bone shield could demolish some decks alone, much more easily than taking tons of pillars, I dare say. If it treats each stack as one chance of picking, not each card in every stack, as the game seems to do, I can't imagine much of a problem.