What about "Convert the cards that are NOT in the 10 decks I have loaded?"
Like, if I 12 unupped Skeletons but 2 are in a deck of mine, make 12 - 2 = 10 so no autoconvert.
Also in the Upgrade menu:
- When clicking on a card, quick check if that copy is needed for one of your decks (10 current loaded decks). If it is, make a warning label saying "You need this card for your DeckNameHere! Are you sure you want to sell or upgrade it? Click on this card again if you are.". This label only appears once per card per time you enter this menu. Example: My deck 3 named "MonoAir" has 6 Wyrms and I have 7 copies. When clicking for the 2nd time on the Wyrm to sell it, this label appears.
- When clicking in the Upgrade or Sell button, remove the extra copies from the decks that have them. In the example of before, my deck will have 1 Wyrm less.