I have no idea where this came from but let's do this.

I'd be the last gym leader of the game, and with no specific type. Also similarly to Kanto's og 8th gym leader, I would be in an earlier town but come back later because I have other things. No I am not a boss but I might have ties to them, no one knows.

My gym would basically be a twisted version of Ylisstol from Awakening but more expansive with extra rooms (only seen in in game cut scenes)

My version

Schoolgirl: Lissa
Wigglytuff
Mightyena
Azumarill

Ace trainer 1:Chrom
Gallade
Aegislash
Minun

Butler: Frederick
Flareon
Empoleon
Ursaring

(Now here's were things crossover)
Ace Trainer 2: Berkut
Sylveon
Tyranitar
Houndoom

Youngster: Anthony
Luxray
Mimikyu
Haxorus

TIME TO BATTLE!

You are challenged by Gym Master Ariel!

Yes I am decked out in Fe cosplay, that goes along with my theme. Keeping within my theme, I don't have a specific team, hell you might double battle me.

Pokemon

Unown Y (Perfect ivs in special attack and speed) Hidden power: Ground, Level 50

Riolu (The ace,Male) Aura Sphere, Ice Punch, Thunder Punch, Shadow Claw, Level 55.

Feraligatr (Female) Ice Fang, Hydropump, Earthquake, Toxic, Level 53

Serperior: Leaf Blade, Double Team, Leech Seed, Swords Dance, Level 53

Arcanine: Flamethrower, Fire Blast, Outrage, Dragon Pulse, Level 52

If you can defeat me, you will receive the Emblem badge (the shield of seals)

After you defeat the elite 4, you can come back and fight all of my pokemon, raised 10 levels.