Why has no one every tried this, I've only found one story that has, so basically we have the characters, being Ashs travelling companions, be they temporary or not, Professors of the regions, champions, being like Cynthia, Alder, Diantha, who were relevant in the show, Rivals, including the likes of Tobias, as well as movie characters like Melody, the legendary pokemon that allied with ash and his friends(telepathy), and of course Ash himself, from some point in the sun and moon anime.

They watch episodes relevant to Ashs character, pokemon, as well as the development of other characters like Team Rocket episodes when they show backstory, or when they encounter James family.