Batman: Arkham Knight's not a game built for modding but that's not stopping dedicated PC players. Tchi6 has managed to make a mesh-swapper tool, letting you play as characters besides Batman in Arkham Knight, Arkham City, and Arkham Origins.
After all, why would you take to the skies of Gotham as fake bat/human Bruce Wayne when you could instead play as the real bat/human Man-Bat.
Man-Bat is a perfect choice of character to show off the tool. The guy already has wings so it makes sense when he dives off a building, spreads his arms, and glides to the ground. Though, I wish the video had shown off a selection of other, less floaty characters; I want to see a flying Commissioner Gordon.
According to the YouTuber who uploaded the mod, "This mod allow us to mix the meshes of EVERYTHING in the game, playing as NPCs, VILLAINS, even CREATE our OWN character, with the set of skills we want."
Creating new characters will be a challenge because they will need to rigged and exported into a format the game will accept but, until then, we've access to every character in Arkham Knight's considerable roster.
You can find the download and instructions for how to use the mesh switcher in the description of the video embedded above.
It's not quite Gordon but here's a video of a gliding Bane in Arkham City.
As ever when installing mods, run the download through a virus-checker.