Persona X Pokemon
You get to choose between all 7 MCs (including Kotone) as your main character.
You would have to go to many regions taking down all the 8 badges in that region, taking down the e4s (It's gotta be a long ass game some way)
each region is related to each persona game (so 5 regions)
your rival/champion in that region would be the main villain from that persona game (Adachi for the p4 region, probably shido or akechi in the p5 region)
each region has some dumb non canon thing about how pokemon are in their universe
You can fuse pokemon to make new ones,and you can also talk to them to make new ones.
you can also have yourself and 3 other pokemon in a battle
... My idea sounds pretty retarded.. but I like both series a lot... and I'm super sleepy so Idk what the fuck i made up..