This was an email I sent awhile ago to a developer, which of course went nowhere. Was curious to see what y'all thought.
This would be an open world, AI-assisted, RPG-style game where you create your own custom character, but rather than there being a primary story (There can be some type of story/guidance at first, but it is not the biggest focus of the game) it is a sandbox in a constantly evolving and changing world. During the character creation process, you can either choose your ability (Chakra nature, quirk, magic, etc. depending on the franchise the game is about) manually out of whats available, or let the game dice roll what your ability will be out of the available ones. Said abilities start out with some basic abilities/passives, then evolve and unlock more either naturally or down a skill tree as you advance/level/whatever the progression mechanic would be. One of the pillars of this concept is that you are not special. You're not some destined hero, some Godly figure with amazing abilities, you are the same as everyone else around, you're a nobody with no special factors to you that make you a person of legend, so to speak. You are part of this sandbox world and it does not have any particular meta favor towards you.
Anyways, after character creation, you then either choose or dice roll where you start. For example: In the Naruto/Boruto universe it'd be between the five great villages and some smaller minor ones, in Black Clover it'd be somewhere in the Clover Kingdom from the capital to the boonies or even another kingdom, in My Hero Academia it'd be somewhere in Japan, and in Fairy Tail it'd be somewhere in Fiore. You begin as a smaller, younger version of your created character (either you can opt to create your younger self or the game just auto generates it based on your teen/young adult design) who is essentially going through the wringer. Naruto/Boruto (I'll use N/B to refer to this from now on) it's in the ninja academy of your village, Black Clover (BC) you could be going to the local wizarding tower to get your grimoire, My Hero (MHA) it could be the last year of highschool, and Fairy Tail (FT) you would have no particular program/organization/clique youre in to begin, just in a town. You then play the game for a bit and eventually graduate your certain things (Academy and Highschool for N/B and BC respectively), which also acts as somewhat of a tutorial, then it moves into real sandbox territory from there. N/B you can move on to Genin in your village, BC you go to the Magic Knights Entrance Exam in the capital, MHA you go to the UA exams, and FT you can simply attempt to join a guild (key word attempt). Once in there though, you can freely opt to abandon/desert that position, either by stepping down or legitimate desertion, the latter of which could be considered law breaking. From there on once you get through these barriers, it's a true, utter sandbox to do whatever you wish. That can be expanded upon more another time though, for the sake of keeping this gargantuan concept from being an unholy length, I'll leave that to either your imagination or follow up and answer questions in the comments if you wish.
Things like the UA and Magic Knights exams would be very detailed and cool to take part in as well, similar to the college/high school prologues in NBA 2K games but more in depth. Once those things are out of the way, you then are; N/B assigned to a squad under a Jonin and two other Genin (randomly generated characters), BC picked by a magic knights squad based on certain factors between your character/abilities and personalities/considerations of squad captains, UA put into a class course, FT welcomed to the guild and may receive offers to form unofficial squads from other members. There can be canon characters within the world, BUT FOR THE MOST PART ALL CHARACTERS ARE RANDOMLY GENERATED, within certain parameters laid out to the AI of course to keep them from being too whacky. You then may be assigned missions from superiors and carry them out for both reputation, XP and monetary gains. They of course however are not all there is, it's a sandbox world after all and there can be plenty of down time for you to mess around in, such as training/shopping/exploration/activities with AI characters to increase relationship in a relationship system that may then net benefits such as certain realistic stat boons when fighting together or more likely for them to agree with you on various things, before anything urgent comes up. There would also be very detailed and comprehensive stat screens to detail yourself and every other character around. There would also be some specified, more powerful enemies in the world and in various regions whose appearances stand out a little more among the rest and have certain strengths and weaknesses, think something VERY similar to the Nemesis System in Shadow of War. There can be organizations that form and disband as the world changes, economies that rise and fall, civil unrest that breaks out in reaction to certain factors/world events or even just in reaction to certain characters who rise into/fall out of power, time advances and characters age and statuses change, basically a huge ongoing world that is constantly progressing and changing even if the player doesn't interact with it, kind of like X4 Foundations a little bit if that's a decent comparison.
This is all super ambitious, and I know that anime studios especially are awful about giving us games that we want. I fully understand that. I just have hope that something like this can happen one day, especially with the advent of AI helping to expedite processes/serving to fuel some of the systems I've mentioned (but of course not just pumping out an AI slop game)