As stated previously, Gyarados is a very interesting Sweeper, transforming the Elite 3 into the Elite 3,5. With this given set, it turns Kyla into an absolute joke.
Gyarados @ Life Orb / Miracle Seed
Ability: Moxie
EVs: 252 Atk / 4 Def / 252 Spe
Jolly Nature
-Aqua Tail
-Custom Move [Grass]
-Taunt
-Dragon Dance
Lead this Pokémon agaist Kyla. Turn 1: use Taunt. Turn 2: use Dragon Dance. Turn 3: sweep and win. Moxie boost will make sure the Custom Move will K.O. Mega Slowbro. After a Dragon Dance, Gyarados is just outside the range Blaziken can reach after one speed boost.
Against Eduard, it can work the same way. However, it’s Rotom-W is quite annoying. You can still prevent Hippodown to place its Stealth Rock, but I don’t know if you really OHKO Rotom at +1 with the Custom Move. Aegislash can also be problematic as you have only contact moves.
For more info on Gyarados as a whole during the adventure, look at this.