My Gym would be the final Gym as a powerful big team. (People think bug is weak so I’m about to prove them wrong.) I would give the player a choice to face me in a single or double battle. Each with their own unique teams and synergies.
My Gym
Double Battle
Ribombee @ Focus Sash
Ability: Shield Dust
EVs: 4 HP / 252 SpA / 252 Spe
Timid Nature
IVs: 0 Atk
- Pollen Puff
- Stun Spore
- Reflect
- Light Screen
Galvantula @ Focus Sash
Ability: Unnerve
EVs: 248 HP / 8 Atk / 252 Spe
Hasty Nature
- Sticky Web
- Electroweb
- Lunge
- Protect
Volbeat (M) @ Focus Sash
Ability: Prankster
EVs: 252 HP / 4 Def / 252 SpD
Calm Nature
IVs: 0 Atk
- Tail Glow
- Baton Pass
- Tailwind
- Sunny Day
Masquerain @ Choice Specs
Ability: Intimidate
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Scald
- Giga Drain
- Bug Buzz
- Air Slash
Volcarona @ Charcoal
Ability: Swarm
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Heat Wave
- Fiery Dance
- Bug Buzz
- Giga Drain
Heracross @ Heracronite
Ability: Moxie
EVs: 252 Atk / 4 SpD / 252 Spe
Adamant Nature
- Close Combat
- Rock Slide
- Earthquake
- Megahorn
This Team would be focused around lowering your stats as much as possible and then send in the 3 heavy hitters in the back. The lead would be Galvantula and Ribombeeto begin setting up. Overall I feel that the best way to tackle this team is to have pivot moves between your strong Pokémon so to never lose momentum.
Single Battle
Araquanid @ Leftovers
Ability: Water Bubble
EVs: 252 HP / 144 Atk / 48 Def / 64 SpD
Careful Nature
- Sticky Web
- Lunge
- Toxic
- Liquidation
Volcarona @ Grassium Z
Ability: Swarm
EVs: 248 HP / 208 Def / 54 Spe
Bold Nature
IVs: 0 Atk
- Safeguard
- Quiver Dance
- Giga Drain
- Fiery Dance
Forretress @ Custap Berry
Ability: Sturdy
EVs: 4 HP / 252 Atk / 252 Spe
Adamant Nature
- Reflect
- Light Screen
- Explosion
- Spikes
Ninjask @ Focus Sash
Ability: Speed Boost
EVs: 252 Atk / 4 SpD / 252 Spe
Adamant Nature
- Protect
- Swords Dance
- Baton Pass
- Acrobatics
Scizor @ Leftovers
Ability: Technician
EVs: 252 HP / 4 Atk / 252 SpD
Careful Nature
- Iron Defense
- Baton Pass
- Bullet Punch
- Roost
Beedrill @ Beedrillite
Ability: Swarm
Shiny: Yes
EVs: 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- Fell Stinger
- Poison Jab
- X-Scissor
- Drill Run
This team works like a pseudo baton pass team. Buffing stats and switching to the sweepers. Although Volcarona and Beedril pack quite the punch on their own. This team could be handled with using switch mechanics like Roar and Red card but don’t make that your only strategy.
Anyways that’s my gym. Let me know which team you’d rather face and why. :)