I'd love to be able to have a pin listed in both my collection and my wishlist at the same time. I may be an odd one, but as an example, I own a Star Trek Premium, but I still have it listed in my wishlist because if I ever see an LE on the marketplace near me I'd pick it up in an instant. Unless the game is on my wishlist I don't get market updates when new games are posted.
This also applies to a couple older pins I'd buy a second copy of for parts like Orbitor 1 or Hyperball. Is this a difficult problem to solve on the back end?