Create an Exchange System for Mass Duplicates
Since the Website already tracks everyone's inventory on career mode, I think it'd be neat to have an option where someone can exchange 10 duplicates for 1 random card of the same rarity from the same series, but it'd be a randomly selected from the cards you don't already have in that set.
Example: I have 10 Base Set Staryu (Common) and haven't obtained a base set Caterpie, Vulpix, Pikachu, or Metapod before. The exchange may give me 1 Vulpix.
The rarity can be either the card rarity, or the pull rarity you already established (so it's based more on functional value rather than card value). If a person already has at least 1 of every card of a given rarity in the set they're exchanging from, it'd randomly choose from the cards they have the least of (same example, but say you had 1 of the 4 cards mentioned above and 2 or more of the rest).
I just think it'd give mass duplicates some value without exchanging for cards that are necessarily "better," but that you at least don't have massive amounts of, or any at all.
Thank you again for making such an excellent simulator! :)