Since we have the Warlock and the Alchemist wandering the board, I would love to see an expansion that brings the other characters on the board to life. Specifically, the Mystic, the Enchantress, the Doctor, the Royal Physician (Royal Doctor on the 4th edition board), the Blacksmith, the Farmer, the Healer, the Ranger, the Barbarian, and the Gambler.
Having the Doctor, Healer, and Royal Physician might seem repetitive, but small variations in the game mechanic they use to heal other characters or themselves could easily make all three very different to play. I know that Talisman Island has a download for some of these characters but I personally prefer official releases that have been tested by the pros.
Adding the Sentinel or Black Knight would round it out to 12 characters but I have no idea how to make them into playable characters that retain the flavor of their roles, unlike the other 10 characters. Some of the ones listed were even playable characters in previous editions.
Preferably these would come out in a character only expansion or an expansion that adds to every deck except the already huge Adventure deck as I mentioned in the starter post to this thread.