I'd do Pokémon Legends for each Gen that doesn't already have one.
Legends Kanto can focus on the creation of Mewtwo in Cinnabar.
Legends Johto can focus on the fires in Ecruteak and the creation of the Legendary Beasts.
Legends Hoenn can focus on Groudon and Kyogre's rampage and how folks needed to survive their endless encounters before they fell asleep.
Legends Unova can focus on the tale of how Kyurem, Reshiram, and Zekrom split.
Legends Alola can focus on the Pillager of Light, who plunged Alola into darkness and required the four guardians to banish him.
Legends Galar can focus on the chaos of the Darkest Day.
Legends Paldea can focus on either the past or the future, where we get to see where the Paradox Pokémon come from.