In addition to being Batman, this mod from Wastelander121 and MrJAG allows you to play as Red Hood, Harley Quinn, Nightwing, Robin, Azrael, Bruce Wayne, Catwoman, Commissioner Gordon, GCPD Officer Owens, and The Joker. The change naturally only applies to the free-roaming sections of the game, and not during the main storyline, since it does not replace prerendered scenes and dialogue.
Many of these characters are playable in limited sections of the game, such as Harley Quinn and Red Hood in preorder bonus missions, or Nightwing and Robin during special Dual Play battles where Batman gets to fight alongside an ally. The mod, then, was simply a matter of unlocking these models and animations for playing around during the rest of the game.
Batman: Arkham Knight is Rocksteady’s recently released culmination of the era-defining action series it began with Batman: Arkham Asylum. We loved playing it on PlayStation 4, but as lovers of the PC as a gaming platform share your frustration with the terribly implemented port. Rocksteady has assured fans that it is hard at work to correct its mistakes, so we hope that soon PC gamers will be able to join us in this fantastic romp through the rain-slicked streets of Gotham.