One thing I could see going in Gladion's favour is that the league is trying to bulk up on character dynamics, having duos and combinations that weren't often tried before. They already beefed up Kiawe and Gladion into legit rivals despite barely interacting before, so maybe something between Gladion and Kukui could happen.
Of course the fact he is fighting for his father could easily just lead up to a vindication story with Guzzlord, with Mohn actually being part of the whole thing. Winning a league would be small potatoes to actually getting him back after all.