You’re a big shot trainer going to open your own gym. What will your theme be?
Personally, I’d go with a haunted house for the gym. Fake ghost pokemon props giving ppl jump scares, mixed in with real pokemon. Except all my pokemon would be fighting type pokemon dressed up like ghost type pokemon.
Ash: “Haha oh what a jump scare! That’s a really fake looking Gengar puppet.”
“Oh now that one looks more like a Gengar.”
Hitmonchamp uses Mega Punch. It’s super effective. Ash gains concussion.
I like water types, and there are a few dual type mons that bring in some type advantages to counter what one would typically bring to a water-type gym (e.g. Palpitoad/Seismitoad and Marshtomp/Swampert are all water/ground to nullify electric types, or the Lotad line to avoid grass-type weaknesses).
As for a gym theme, I like the idea of a spa/thermal baths place that functions as the town’s Pokémon Center, with a closed off area for gym challengers. Gym leaders are often important members of the community, so I think it makes sense that the gym leader would have other duties to their town in addition to battling.