A complete reboot of the show, Kanto redone in Alola.
Ash is still the main character, a new Ash starting out on a new journey and a new voice actor to reflect this. This new Ash is basically the same, but with a different goal---he'd have a ton of human friends before starting out on his journey and his goal would be to befriend 150 Pokemon. This starts with an injured Pikachu he finds at his school, and then he makes that his Starter and sets out across Alola. He'd have a primary set of Pokemon, including all three Alola Starters, but would catch many other Pokemon he'd rotate in and out occasionally from among the other 721 Pokemon. They'd hang out at his mom's who'd own a bar, like she did in Shudo's novelizations.
Brock and Misty are his companions, but changed up and with new voice actors. Brock is a hapless salary man bored with life, except when it comes to chasing after women, and is reinvigorated by seeing Ash's youthfulness. He'd have a secret desire to be a Pokemon Breeder that would've been forgotten years ago, but would remember it when meeting Ash. Misty is more of a tomboy and the daughter of a fisherman who disappeared years ago, she'd be traveling around Alola looking for him and meets with Ash and befriends him, with some romantic attachment perhaps. There'd be some new large Water-type Pokemon she'd own that'd ferry them across the island.
Team Rocket return, and are the only characters who keep their original voice actors but have slight visual designs, James has a ponytail and Jessie has a pixie cut. Meowth is a bit more sly and crafty here and begins as a spy sent by Giovanni to watch over the two, but slowly warms up to them. Giovanni here would in reality be a young boy, the son of Madame Boss, who inherited Team Rocket following their dismantling previously and J&J would be his only agents at first as he tries to rebuild.
Outside of that the story would be different from Kanto and reflective of S&M's plot.