We really wanted to add a fifth player so we decided to play with the Level 2 cards and manually track the fifth player (hey, wanted to include my wife in the game with my two oldest friends and my son). It's worked pretty well so far. We've felt challenged and have had characters KO'd. It's a lot like it was when we played Level 1 monsters with just the four players. It's a big of administration to track everything outside the game for the fifth players but we've had a good time so who cares?
Curious about how others have handled this kind of thing. We'd love if the app allowed for manual ads of items, but realize that might be out of scope of the app.