The PC version of Batman: Arkham Knight is a bit of a mess at the moment, but it’s also the only version with a mod that allows you to swap between any playable character in free roam with the push of a button.
Tired of playing as Batman? Press F2 and play as Harley Quinn, the crazed anti-hero on a quest to make up for bad DLC. Or F1 to clean up the street of Gotham City as the Red Hood, ultra-violent vigilante with surrogate daddy issues. There are ten additional characters in all, several of which I will not list as to avoid spoilers.
Warning—the video linked below as well as its YouTube description features character spoilers for Batman: Arkham Knight.
Between mods like this and Rocksteady’s ongoing patches and fixes, perhaps one the PC version will be remembered as the ultimate haha. Sorry.