I'd like a Bug leader as the end challenge since usually the game's make Bug gyms out to be a throwaway, early-game cheese; there are sincerely intimidating Bugs out there, like Scizor and Volcarona, that can be played with in regards to a Bug master vying to be a legitimate threat.
+1 to this; exactly why I put it last in the line-up. Also,
yeeeee my line-up was chosen!
Psychic
Piggybacking off my list of why I chose the types in the first place, I imagine this one would be a real spiritual
(Granola Girl) type. Pokemon always portrays psychic-specialists as calm badasses or gifted, plucky kids, so I think an early psychic gym with a peace-and-love, dreadlocked, earthy, tarot-card-reading, gem therapist would be a nice change of pace. Her gym could be the back room of her shop that sells soaps and candles and stuff leaning on the occult. Maybe a quartz theme would do well here. Her inspiration comes from the strong ties to the moon in many different spiritual and religious practices. Here's an image reference:
Dark
Maybe a nomadic, mysterious type? Or a friendly, reserved, nurturing type that loves nursery rhymes: subverts expectation, and there's a "man in the moon" thing here somewhere.
Rock
Haha, what if they were a dairy farmer who makes a special world-famous cheese. Could be a jumpy personality 'cause the cow jumped over the moon, ayyyyy.
Ice
Anything that isn't methodical or beautiful in approach. Something that incites fear in the opponent about hypothermia and accurately represents the threat winter has on your health.
Fairy
Just to subvert the mystical
pretty in pink theme fairies have, why not have a conspiracy theorist/paranormal investigator type? Or a secret-government-police bloke? They'd be all paranoid about aliens and UFO crash sites.
X-Files jargon, obsessed with the
Illuminati. His gym would be Area 51. Basically what I'm saying is make Mr. Crocker from
Fairly Odd Parents a Men In Black, and throw in traits of Dib from
Invader Zim.
Steel or Flying
Robotics? Satellites? Anything to get a NASA or space-race theme in here. I'd love to see an anti-gravity battle. Leader could be an astronaut, or an engineer, or maybe someone based off one of those BAMF mathematicians like Katherine Johnson?
Bug
A B-Movie horror edge would be so fun here. Like, they could be a foreign movie producer/director with a thick mustache that makes schlocky "Plan 9 from Outer Space" and "The Thing" expys involving bugs. Could have his gym be a movie set. Something to get away from the youthful, spring theme bug-specialists have. He calls out all his commands through a megaphone and films his battles too, lol.