>>34635269Gym leaders and elite 4 use items and have a full team. Elite 4 members also have a pokemon that can mega evolve and one that can use a Z move. They also have teams with max IVs, proper EV spreads and beneficial natures for all their pokemon.
Have the Champion have all the boosts that were previously exclusive to the player, i.e, things like the Refresh bonuses where their pokemon might survive attacks, have higher critical hit ratios and dodge attacks.
Regular trainers can carry between 1-4 pokemon, ace trainers always carry 5 pokemon with one that can use a Z move and veteran trainers always carry a full team with one mega pokemon.
If gyms return have them function like the trials where if you exit the gym you have to start over again. Also have trainers switch out their pokemon if they're at a disadvantage against yours.