>>44249672I know, he shows up once on Akala Island then promptly fucks off until midway through Ula'Ula Island where if you didn't guess he was Lillie's brother he makes it painfully obvious by reminding you and Hau to protect Lillie and Cosmog, then he fucks off until Lillie gets kidnapped and during that time seems to have left/abandoned Team Skull.
Then there's the entire question of what exactly was he trying to achieve by working with Team Skull, he just talks about getting stronger without coming to an epiphany as to how to achieve that, he just has a change of heart I guess. Also if him stealing Type: Null was one of the big issues that he effectively abandoned the Aether Foundation how did Lusamine not know he'd joined up with Team Skull, there is never a hint in the game that Team Skull is even aware of Gladion's ties to the foundation.
They honestly should've had him acting as a lone entity in the game entirely separate from Team Skull, have him interrupt the player's Grand Trial against Hala that way he's introduced earlier, you have it be set-up that he's looking for rare Pokemon and shows knowledge of Cosmog, obviously some people might immediately suspect he's Lillie's brother due to their similar appearance but at least it's not blatantly spelled out for you before being stated in the game, some people may think Gladion is a third-party separate from Team Skull who's after Cosmog.
Use Akala Island to show that he's not working with Team Skull and maybe even have a team-up battle with him somewhere maybe at Wela Volcano Park that way you can give Kiawe some dialogue. At some point in late Akala (Grand Trial against Olivia) you have Gladion realize the player's strength and helps the player from that point forward, you can have the player and Gladion storm Po Town and basically loop back to where he was in Ula'Ula and have him just off-hand remark that he's Lillie's sister it's really not that important of a plot point.