alright this is going to be quite a lengthy post. so I was able to play around with the team and the potential 6th slots and changes as well. I'm also basing all of my responses based on Volcanion as the last slot (Yes I have tried out both Nidoqueen and Tentacruel but, I personally liked Volcanion more since it checks a lot more Pokemon such as Waters, Fairies, and Scizor in one without being a momentum drain) Anyways...
After reading tmacbalanced's post, I'm not too fond of Slowking right now in particular since it seems a bit odd to me find it on an offensive-e team. While I really do think Spikes stacks with Klefki is very solid, I would much rather have hazard removal considering both Mega Aero and Volcanion are checking quite a lot, and having them switch into hazards isn't too ideal.
I liked the idea of swapping out both Klefki and Slowking for both utility Togekiss and Metagross. I feel that if we add Volcanion to the team, it would've overlapped quite a bit since Klefki would check Latias and such while Volcanion checks Water-types. Though HP Fire Latias would be something we would be weak to. Personally, I think Metagross is probably a nice substitution since we have a nice Dark check with Klefki / Togekiss and Conkeldurr, and it is able to check Latias and also act as a secondary Fairy check (it helps a lot against a weakness against CM Clefable) which helps alleviate some stress for Volcanion.
Metagross @ Shuca Berry / Colbur Berry
Ability: Clear Body
EVs: 236 HP / 96 Atk / 176 Spe
Adamant Nature
- Stealth Rock
- Meteor Mash
- Earthquake
- Pursuit
I wasn't able to test out these last few Metagross sets but, I could the Expert Belt set being pretty decent to lure in Swampert specifically and other Water-types with Grass Knot, not sure how I feel about it since we lose Pursuit (which I find pretty necessary since Metagross is a better Latias Pursuit trapper than Mega Aero). It's an option nevertheless. Also I'm not sure who came up with the set, I just remember seeing CrystalFalchion using it during week 1 of RW.
Metagross @ Expert Belt
Ability: Clear Body
EVs: 220 Atk / 112 SpA / 176 Spe
Naughty Nature
- Meteor Mash
- Earthquake
- Grass Knot
- Stealth Rock
As for Assault Vest, this was the set I would've used. I probably wouldn't use it since the EVs were pretty random honestly. Anyways, Assault Vest Metagross was meant to be paired with Stealth Rock Mega Aero (Rocks / Stone Edge / EQ / Wing Attack or maybe Ice Fang / Aqua Tail since Gliscor could be annoying?). Assault Vest provides Metagross an even better matchup against offensive Celebi, Fire Blast Clefable, and HP Fire Latias at the expense of like having no speed (which can be fixed) and a worse matchup against Dark / ground types without a type resist berry. If we do decide to go with this set, entry hazard removal is a must since Metagross will get worn down quite easily.
Metagross @ Assault Vest
Ability: Clear Body
EVs: 252 HP / 252 Atk / 4 SpD
Adamant Nature
- Pursuit
- Meteor Mash
- Bullet Punch
- Earthquake
So enough about Metagross... As for Togekiss I believe a utility set can replace Klefki. Togekiss also helps check Fighting-types (mainly like Keldeo and Heracross, but it will provide a better matchup to threats like Bewear and Infernape better than Klefki). Conkeldurr can be a little problematic depending on whether or not it has Band / Poison Jab / Ice Punch. Anyways, Togekiss provides the much needed entry hazard removal, considering we have 1 (potentially 2), stealth rocks weak Pokemon. I don't find Nasty Plot necessary considering Haxorus is already a very solid stallbreaker so yeah. Also I'm not too sure if utility Togekiss is even good on offense, I personally found it quite nice (I remember seeing either Shiba or Eyan bringing it up at one point).
Togekiss @ Leftovers
Ability: Serene Grace
EVs: 252 HP / 160 Def / 96 Spe
Bold Nature
- Air Slash
- Heal Bell / Thunder Wave
- Roost
- Defog
Lastly, since JoarAddamNessosin kinda made the Volcanion set a toss-up, I found Z-SolarBeam probably the most effective. Z-Solarbeam helps our matchup against Water-types (specifically bulkier ones) such as Slowking(bro), Suicune, and Mega Blastoise. Not much to say other than that lol, I just found that Choice Specs sets were easily taken advantage of if Volcanion locked itself into HP Electric or Sludge Bomb by Pokemon like Nasty Plot Celebi, Cobalion, and CM Latias. Leftovers recovery was nice but, I liked the spike in power with Grassium-Z more.
Volcanion @ Grassium Z
Ability: Water Absorb
EVs: 252 SpA / 4 SpD / 252 Spe
Modest Nature
- Steam Eruption
- Fire Blast
- Sludge Bomb
- Solar Beam
Anyways thanks for reading my wall! I'm actually considering extending the deadline by a day to get more input on the laundry list of changes ^^
oh yeah, I'll also encourage everyone to use all 3 submissions and the team and see how it feels for any last minute changes after (or during) this round.
e- just realized this core is weak to both Nidos (I didn't think much about it since I didn't face either while testing surprisingly) but, we have Mega Aero as a check though which might not be enough.