As much as fans craved it, many were shocked Todd Phillips and Joaquin Phoenix's Joker sequel came to fruition. Titled Joker: Folie à Deux, with so much shrouded in secrecy, it's anybody's guess how the plot could go, which is no surprise because Phillips kept details on the first film close to the vest. Regardless, some theorize it could work in other villains alongside Joker and Harley Quinn. However, instead of worrying about who's flourishing in Gotham's despair, a follow-up could be the perfect place for a Nightwing origin story.
A Nightwing story is on the table because Bruce Wayne is so young in this world. Thus, a time-jump to have him as Batman would mean Phoenix's Arthur Fleck would be way too old. As a result, Dick Grayson as a foil would fit, especially if Phillips works in his cop background. That's happened in so many Nightwing stories, from the Titans TV show to his super-spy role in Tom King's books.
That allows Joker 2 to have Dick tracking down what happened to Arthur after the first film ended with the comedian looking to escape an asylum. But seeing as Joker was about corrupt systems in Gotham, Dick can become Nightwing to investigate places his badge won't take him, embodying the detective nature of the Dark Knight. As this vigilante, he can also take out the gangs Joker inspired and give in to the rage, especially if he lost his parents the night of the riots.
It would harness elements of Christopher Nolan's Joker and Titans, where Dick wanted Joker dead due to his shifting moral compass. And crossing the line would even nod towards Jason Todd's journey as Red Hood. That can test Dick's view of justice, as he struggles with how oppressive and brutal cops can be, carving out sociopolitical commentary on a deeper level. And such a direction would be more nuanced than rich guys suiting up to cleanse their conscience in the name of revenge.
In the process, Phillips can chart something gritty and elucidate Nightwing's inner demons like Matt Reeves did with his Caped Crusader. It'd also allow Warner Bros. to skip the campy Robin story for something more grounded, cerebral and in-line with the nature of the current Bat-family. And that's not even mentioning that it solves the longstanding issue the studio has had with getting Chris McKay's Nightwing off the ground.
With Joker 2, there's no DC Extended Universe continuity to worry about. All that matters is giving Phoenix's Joker room to be a nuanced villain, which he can do by trying to break the symbol of law enforcement. And ultimately, as Nightwing fights off the notion that fire's the cure for society, it can motivate a Batman to join the crusade.