>>29102062Just make rivals level up with you and have as many pokemon as you do. Also make it possible for them to beat you and the story can continue, but can rematch with them anytime. This will make it feel like they're your actual rival, someone who matches your skill, and not some kid following you around.
Maybe even give some extra dialogue depending on the current win-lose ratio. Playful if they have more wins, determined if they have more loses.