With Arkham Knight being Rocksteady's Final Batman game, I feel now
would be the prime oppourtunity to give an appearance to a lesser known, but excellent Villain. The Phantasm. I personally feel that the Phanstasm is one of the Caped Crusaders most menacing foes, and though short lived, has had a huge impact on the franchise. Not only would the Phantasm fit right into the dark grim setting of the Arkham games, it would be an excellent chance to put some of the most of the more overused villains to rest for the series.
Though the Joker is gone, it is undeniable that he will appear in flashbacks, the Scarcrow Gas segments, or some other way as a cameo. Bane or Killer Croc would be prime candidates to replace. Both have appeared in all three Arkham Games so Far. And haven't had much reason to be.
Victor Zsaz is another prime candidate. Having appeared in two out of three games so far, he's served as tutorials and a side mission that while interesting narratively, didn't add all that much.
I know the Phantasm wouldn't fit in with Scarecrows grand plan, but a side mission would be Featuring her would be a welcom addition to the Franchise. Especially given Arkham's ties to the Animated Series, through the voice actors.
So who else would like to see the Phantasm in Arkham Knight? Who would you like to see her replace? If she were to appear, what would you like her side mission to involve?