You're not suppossed to keep Gourgeist in when a special attacker is out. Physical walls don't wall special attacks. If they did, they wouldn't be physical walls. So what you wanna do instead is add a special wall/tank to your team. There's Blissey/Chansey, Tyranitar, Goodra, and Sylveon, to name a few.
-Blissey w/Leftovers
Nature: Calm
Ability: Natural Cure
EVs: 252 Sp.Defense, 252 Defense, 4 HP
Moves: Softboiled, Aromatherapy, Flamethrower, Toxic
-Chansey w/Eviolite
Nature: Bold/Calm
Ability: Natural Cure
EVs: 252 HP, 252 Defense
Moves: Softboiled, Aromatherapy, Toxic, Seismic Toss
-Tyranitar w/Assault Vest
Nature: Sassy
Ability: Sand Stream
EVs: 252 HP, 252 Sp.Defense, 4 Attack
Moves: Payback, Pursuit, Stone Edge, Superpower/Brick Break
-Goodra w/Assault Vest
Nature: Modest
Ability: Gooey/Sap Sipper
EVs: 252 HP, 252 Sp.Attack, 4 Defense
Moves: Draco Meteor/Dragon Pulse, Flamethrower, Sludge Bomb, Thunderbolt
-Slyveon w/Leftovers
Nature: Bold
Ability: Pixilate
EVs: 252 HP, 244 Defense, 12 Sp.Attack
Moves: Hyper Voice, Wish, Protect, Heal Bell/Toxic
or
-Sylveon w/Leftovers
Nature: Modest
Ability: Pixilate/Cute Charm
EVs: 252 HP, 252 Sp.Attack, 4 Sp. Defense
Moves: Hyper Voice/Moonblast, Shadow Ball, Calm Mind, Psyshock/Hidden Power Fire
Also, Surf or Hydro Pump is better on Greninja than Scald. Scald is for Pokemon that can take a hit. Greninja is not one of those pokes. It needs as much power as possible.
Jolteon is better suited to rain teams where it can spam Specs Thunder and its teammates can easily handle the stuff that resists or is immune to Thunder. Otherwise its not that great since its very frail and has a movepool as deep as a kiddie pool.
So for Jolteon's replacement, you could put Talonflame in there like
Nymphadora Peitharchia said. Or a special attacker. But idk what to put in atm.
Perhaps I could add in a special wall for the sixth slot, most teams people bring in battle spot are mostly composed of physical attackers but when they have at least 1 special attacker when I use gourgeist, they switch to their special attacker and Will-O-Wisp/Leech Seed hit them, then next turn it's mostly a bad idea to swith out Gourgeist because one of my attackers might faint against the attack that the special attacker uses. Maybe I'll throw in a special wall or replace gourgeist with a mixed wall. Also I think I'll keep Jolteon to see how it works out to, it's really fast and with Choice Specs, does a lot of damage, can usually survive 1 hit from special attackers but against physical attackers it faints. I put it on my team to deal with Gyarados, Azumarill, and other water types, can also deal with dragons and ground type pokemon with hidden power ice otherwise just get away with volt switch and put out a wall. For Greninja, I picked Scald because of the 30% chance of burn and hydro pump's accuracy is 80% which makes it miss sometimes which leads to losses, Surf might be a better idea, idk. Talonflame is a good one to :)
Thinking of replacing gourgeist with sableye/klefki/cresselia or keeping it and using sylveon for the last slot. Talonflame is pretty good to, also might use it for the last slot.