I've been on a pokemon AU mood as of late so I might as well expand the cast and assign Gym Leaders. Each gym has it's own gimmick that gets more hindering the higher up the trainer goes.
1st Gym: Ross (bug) - the main trio's teacher. They challenge his gym on their way out of the university city as the final test to formally begin their journey. His gym is in the school and the challengers fight their fellow students tournament style, that way he can get through multiple students at a time. A lot of pokemon in this gym has moves that lowers atk, sp.atk and accuracy.
2nd Gym: Noa (normal) - a classmate who moved back to his hometown. Instead of challenging gyms, he straight up promoted in his hometown after he graduated. He will never live the lazy bum life he wanted. His gym is just his mansion and he literally lives there. The goal is to get to his bedroom to wake him up as the challenger fights his servants. Lots of stalling tactics with protect and substitute and sleep and rest in his servants' team movesets.
Occupation: Scion, Student
TM: Rest (for irony points as his main Komala can't actually use it and it remains out of reach from him)
3rd Gym: Natalia (water) - the current contest hall master who doubles as the gym leader. Aims to promote her town's tourism with events and commerce through her performances. Her gym is aquarium show based and each round is a stage. Challengers move from stage to stage until they get to the biggest one with Natalia on it. It "rains" all over the gym and it can't be changed. Between Scalds giving burns and all kinds of poison moves, the gym does a lot of chip damage.
Occupation: Contest Hall Champion and Judge, Student
4th Gym: Haruji (grass) - Shizuke's grandmother and the current shrine guardian for a legendary pokemon. Her gym is a grove and each round is laiden with traps that trigger as soon as the fight begins and automatically applies a random status on the first pokemon in line. Uses similar tactics as Shizuke with effect powders and leech seeds.
Occupation: Shrine Guardian, Berry Shopkeeper
5th Gym: Gavril (ice) - Fiona's older brother. He took over the gym after their mom retired to seal away a legendary pokemon. His gym is at a slope where the challengers slide across the slush and fight trainers on the way down to where Gavril is. Snow is a constant and can't be changed. Set ups are also prevented with rapid spin and ice spinner. Pokemon on both sides have a higher chance of getting frozen than usual.
Occupation: Pokemon Racer
6th Gym: Travis (dark) - Zephyr's dad who runs a casino, which is also where his gym is. There's some kind of gimmick that involves slots messing with atk and def stats every time either side loses a pokemon.
Occupation: Professional Gambler
7th Gym: Chihiro (electric) - a flashy girl who's gym is in a tall glass fashion house and works closely with Natalia, trading materials in exchange for her creations. Her gym's got a lot of elevators and conveyor belts. It's similar to Travis' gym when it comes to messing with stats, but hers messes with speed and turns. Every few turns her pokemon gain priority because of the tower's mechanisms. Electric Terrain is also on.
Occupation: Pokemon Accessory and Fashion Designer
8th Gym: Leo (fighting) - Keagan's cousin who went on a pokemon journey a year before. Lost to the champion and ended up as a gym leader. His gym is a flashy stadium. There's a level cap that keeps all pokemon entering the gym stay in that level and Leo's team being ten levels over it.
Occupation: Model, Athlete, Fencer
Next time I'll think of the elite four.