What do you think are the requirements to be a Gym Leader?
Well, there's no explanation about how did trainers get to become a Gym Leader and the requirements for it, but I think the requirements to become a Gym Leader is to start off as a trainer and train pokemon, collect badges and beating Elite Four to win the Champions League. Being a Gym Leader is responsible for training their pokemon for their next challenger and to test the trainer and their pokemon so they can be strong and resourceful to challenge the Elite Four, the Gym Leader is also responsible for making the interior of the gym suitable for their pokemon (Like pools for water-type gym or grass and flower for grass-type gym), every Gym's interior has its own perspective for the Gym Leader's pokemon and they can pass on their main job as a Gym Leader to another family member to keep the Gym running just like Janine, she takes over her father's position as a Gym Leader after he got promoted to the Elite Four.
Oh yeah, I just got Cheren, Elesa, Roxie (Tomika) and Shizui's sprite after the official release of BW 2, but I can't find the pictures of the Toxic Badge and the Wave Badge. So, I'll make Elesa's new look userbar and Cheren's userbar and hold them for a week to wait for the Toxic and Wave Badge for Roxie and Shizui's userbar.