As most of you don't know, at the premiere of Thor: Love and Thunder, Christian Bale revealed that he would be open to starring in a fourth film in the Dark Knight Trilogy, but if only Christopher Nolan were to direct. And here are some storylines and new characters that would be introduced into the series.
The Dark Knight Returns:
In the wake of Batman's "Death", John Blake becomes the new protector of Gotham City after failing to convince Bruce Wayne to come out of retirement. However, when a new villain, Harley Quinn comes to Gotham, seeking revenge against Batman after the Joker's death and works with Scarecrow to finally uncover who Batman really is, Bruce Wayne is forced back into action and must decide how far he is willing to go to protect Gotham at any cost
New Characters:
Leslie Tompkins debuts as a love interest for Bruce Wayne
New Robin: Damian Wayne, Bruce's son with Talia al Ghul
Jim Gordon's daughter Barbara Gordon who becomes the crime-fighting youth known as Batgirl
New Villains would be introduced:
The Penguin/Oswald Cobblepot: In the Dark Knight universe, he is depicted as being handsome, wealthy, well-connected, well-educated and Bruce-level magnet for the ladies. He secretly hates people and wants to reshape Gotham in his own image, but he is a seductive villain who controls a number of gangs in Gotham, sometimes even going out with them in heists.
Mister Freeze: Victor Fries was a simple worker in the cooling systems of Wayne Enterprises, he blames Batman for not being able to save his late wife in a mugging gone wrong. Mr. Freeze, or Victor is a covert menace, a serial killer whose only ingenuity is being able to hide his deeds from the head of Wayne's board. Certainly not a genius scientist, just a man with a chip on his shoulder and some resources that allow him to put his victims in cold storage and builds a sort of pressure washer/flamethrower which injects liquid nitrogen which is more thought as a scare tactic than a convenient weapon
Poison Ivy: In Nolan's universe, Poison Ivy is a college student, unable to secure funding for her latest science project. So she decides to become an eco-terrorist with a natural immunity who kills for her cause.
The Riddler: Edward Nygma would be portrayed as a former IRA bomber and cypher expert, computer hacker, etc. Each crime he commits would be accompanied by a riddle and there are always 2 answers -- one obvious and one pun. But the answers themselves all add up to a bigger puzzle, the answer to which is in fact a huge red herring to disguise his main objective which is a grand theft of some sort. A war would erupt between him and the Penguin(which the reason being the Penguin killed his family, so he came to the US to exact revenge)
This sequel to the Dark Knight trilogy would act as a proper conclusion of the series as some people felt that the ending of the Dark Knight Rises was sequel bait that never came of anything rather than an actual ending to the trilogy.
https://www.indiewire.com/2022/06/christian-bale-fourth-christopher-nolan-batman-movie-1234736878/