>>54159854Pokemon Origins (the anime for the events of FRLG) showcased this with Brock; gym leaders will tailor their team based on the number of badges you have. It's heavily implied that these trainers aren't much different from the player character beyond specializing in a certain type, so they likely have a PC box full of different mons of said type. (After all, why would Bill invent a storage system for just one 10 year old kid?)
Sadly, this mechanic isn't implemented in any pokemon game; it would be so much better if they matched the number of mons you have and scaled their levels.
