If this run is done, would I be required to submit it under the current board or will it be possible to have a new leaderboard created. I adore Persona as a series and only recently got into speedrunning. I was thinking the rules could be that Joker is only allowed to use Arsene and the player has to buy back Arsene as soon as possible... or the Run could begin on a certain date after Arsene has been bought back... im really new to speedrunning and dont mod any of the games, so please tell me if something is wrong...

We do not plan on currently adding any new categories that the majority of the community has no interest in. What you're describing is more of a "challenge" run if anything. Of course, in the end you can do or run whatever you want but it won't be added as a category to the boards here.

You could submit an Arsene-only run under the current board, but it would have to be on Hard and fulfill requirements for the True Ending, as well as follow the other rules of the category. So long as it hits those criteria it can be submitted.

But yea like Nev said, category wise as well as there not being any interest it is just too specific of a thing to add. Difficulty and Ending are about the only things that make sense to base categories around, when you start getting into limiting certain elements of the game (like fusions) you get less into a speedrun and more into just a specific challenge run.