I made a video on YT where I list the Pokémon I would have on my team if I was a gym leader and why
Idk what to make so... here we are
Link is below
I get that was your own Pokémon if you had a gym, but if that was a gym in a normal Pokémon game, it would be way too unbalanced. Having all of those strong Pokémon plus a mythical just to top everything off is not something that should be a thing.
Then maybe this would fit better as an elite 4, also it depends on the Pokémon game what level your Pokémon are at depending on how many wild Pokémon are before the gym and maybe right before my gym they could get large access to fire, ground, and fighting types so they would get type coverage