While that scenario is certainly intriguing to consider, it is highly unlikely given the Joker's history of violence, instability, and complete lack of remorse for his actions. The Joker is one of the most iconic villains in comic book history precisely because of his relentless and senseless cruelty, so it would be difficult to imagine him truly committing to a path of redemption. However, if the story were to explore that possibility, it could provide some very interesting themes and character development for both Batman and the Joker.