This is kinda why, if it really does exist, Codename stars to pull a Black2/White2.

Gladion is new president of the Aether Foundation and is actually trying to help pokemon.

Hala has gotten too old and so Tapu Koko chooses Hau to succeed him as Kahuna.

Lillie, finally a Champion of the Indigo Plateau, returns to Alola.

Colress takes on a roll as Villian or Side Villian who plans to once again use Z power to its fullest extent, and maybe even develope his own synthetic Z bracelet and crystals.

Some of the trial captains are the Same, others however got too old and had to hand off their position as captain.

Hapu has fully set into her roll as Kahuna of Poni Island and so keeps the sacred grounds tended to.

Nanu possibly finds a way to get Tapu Bulu to pick a new Kahuna so he can take care of his Meowths and Persion. He's still a cop, but he hasnt found out about the games current villiany.

Guzma returns after having trained with Hala, having his life back on track but still mischevious, maybe work as a trickster mentor type.

this is a long comment.