SM OU Looking for alt mons to switch into my team

[Brezmon]

So I'm kinda new at team building and all that good stuff so this team isn't too complex just wanted to know if its any good or what Mons would fit in better. I've been having success with it but I'm low enough on the ladder (about 1300)

vegetables (Ferrothorn) @ Rocky Helmet
Ability: Iron Barbs
EVs: 248 HP / 8 Atk / 252 Def
Impish Nature
- Stealth Rock
- Leech Seed
- Toxic
- Knock Off
(Pretty standard defensive wall he's a pretty nice switch in for nice chip damage)

wingman (Zapdos) @ Leftovers
Ability: Static
Shiny: Yes
EVs: 252 HP / 252 SpD / 4 Spe
Timid Nature
- Discharge
- Heat Wave
- Hidden Power [Ice]
- Roost
(This is my SpD tank I've tried running defog but I find I use HP ice more often maybe its just the elo I'm in)

Beefcake (Mamoswine) @ Assault Vest
Ability: Thick Fat
EVs: 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- Ice Shard
- Earthquake
- Knock Off
- Iron Head
(This is my answer to fairy and fire types he can usually eat a fire attack and kill with eq)

Ggwp (Greninja) @ Choice Scarf
Ability: Protean
Shiny: Yes
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
- Dark Pulse
- Grass Knot
- Ice Beam
- Taunt
(So this guy is my revenge killer and sometimes my lead if I know a lando will be leading)

Trump (Staraptor) @ Choice Scarf
Ability: Intimidate
Shiny: Yes
EVs: 252 Atk / 4 Def / 252 Spe
Jolly Nature
- Brave Bird
- Close Combat
- U-turn
- Tailwind
(Another revenge killer and sweeper, I gave it tailwind to setup sweeps if I can sac it off)

Uhoh (Diancie-Mega) @ Diancite
Ability: Magic Bounce
Shiny: Yes
EVs: 4 Atk / 252 SpA / 252 Spe
Hasty Nature
- Substitute
- Diamond Storm
- Moonblast
- Earth Power
(I just swapped this in havnt used it much I usually use medicham or gardevoir. Medicham is nice with a tailwind behind him)

 

[Diophantine]

Hey Brezmon I'm not sure if this counts as a proper RMT since you haven't given that much description/explanation, but I'll try to help the team anyway.

First off, we should decide what this team hopes to achieve. I think "Basic Bulky Offense with Protean Greninja and Mamoswine breaking down or pressuring common defensive cores that allows Diancie to sweep" is a good theme to stick by. We may change this later on, but let's have this in mind initially.

I'd make Ferrothorn Specially Defensive and Zapdos Physically Defensive. Ferrothorn being SpDef means that it's a better check for Battle Bond Greninja, Magearna, Mega Alakazam and many more (which Zapdos has trouble with). Here is the set I would use:

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vegetables (Ferrothorn) @ Leftovers
Ability: Iron Barbs
EVs: 248 HP / 52 Def / 208 SpD
Careful Nature
- Stealth Rock
- Leech Seed
- Power Whip
- Thunder Wave

Stealth Rocks because it's your designated Stealth Rocker. Leech Seed is nice to chip things as they switch in or but certain things on a timer while also giving Ferrothorn extra recovery to check more things in the game. Power Whip is to kill Greninja/Tapu Fini/Keldeo (if you're comfortable with taking the hit). Thunder Wave is for Kartana that may think it can come in and render Ferrothorn useless (which most Ferrothorn are against a Kartana). I used this over Hidden Power Fire because I think T Wave is useful in many other scenarios.

We now need something for the physical attackers and I know you like Zapdos (who doesn't it's one of my favourites too) so let's make this something to punish physical attackers like Pinsir and Hawlucha.

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wingman (Zapdos) @ Leftovers
Ability: Static
Shiny: Yes
EVs: 252 HP / 232 Def / 24 Spe
Bold Nature
IVs: 0 Atk
- Discharge
- Heat Wave
- Hidden Power [Ice]
- Roost

I gave it the EVs in Speed to outspeed max speed Adamant Mega-Tyranitar (if it's not Dragon Dance, you can make it waste its Stone Edges by Roosting in its face if you're not at full HP) and Bisharp.

Next I'll move onto the Mamoswine. I'm a big fan of Mamoswine in this metagame because of how much pressure it puts on teams not running Mega Scizor or some sort of Tapu Lele offense. Here's a set I would use on this team:

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Beefcake (Mamoswine) @ Life Orb
Ability: Thick Fat
EVs: 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- Ice Shard
- Earthquake
- Knock Off
- Icicle Crash

I added Icicle Crash for powerful Ice STAB and I gave it a Life Orb to maximise damage output (as this is what we're intending for it to do). Another option is Superpower over Knock Off, but I think that Knock Off is better in most circumstances.

Just a brief technicality: all Greninja should be male and non-shiny. This is because Battle Bond Greninja can only be male and non-shiny (sucks, I know - shiny Greninja looks badass). If Greninja is female or shiny, your opponent immediately knows what to expect, and information gathering is a very important thing in Pokemon. I am actually going to replace Greninja as, at the moment, we do not switch into Heatran at all. I am going to replace it with Calm Mind, Taunt Waterium-Z Keldeo. This gives us a better option against stall while still managing to break holes for our sweeper.

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Keldeo-Resolute @ Waterium Z
Ability: Justified
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Hydro Pump
- Taunt
- Calm Mind
- Secret Sword

We now need a form of speed control, since Greninja is our fastest Pokemon. A scarfer should do the job. Looking at our team, we have no way to deal with Volcarona other than getting rocks up and hoping we can outplay to the point where we don't allow it to get a boost (which is unlikely). I think a scarfer that can revenge kill Volcarona at +1 speed while also providing momentum is a good option. Tapu Koko isn't usually a scarfer, but I think it works here.

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Tapu Koko @ Choice Scarf
Ability: Electric Surge
EVs: 252 Atk / 36 SpA / 220 Spe
Naughty Nature
- Wild Charge
- Volt Switch
- Brave Bird
- Hidden Power [Ice]

The nature and EVs is so it outspeeds base 110 speed Pokemon with a Choice Scarf like Latios, Latias and Gengar (though uncommon). If you wish to outspeed Choice Scarf Greninja, then this is the set I would use:

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Tapu Koko @ Choice Scarf
Ability: Electric Surge
EVs: 252 Atk / 64 SpA / 192 Spe
Naive Nature
- Wild Charge
- Volt Switch
- Brave Bird
- Hidden Power [Ice]

I put the excess EVs from the speed we don't need (in both sets) into Special Attack for Volt Switch, but you can put it into HP if you want for the possibility of more Brave Bird/Wild Charge usage.

Finally, let's look at Diancie. I am going to remove Substitue off of Diancie, as Diancie's subs are not that big given its low HP and we can make way for another coverage move. I am going to stick with the 3 attacks you mentioned, but I am also going to add HP Fire for Ferrothorn. Alternative options include: Nature Power (in electric terrain acts as a STAB Thunderbolt allowing for better damage on Celesteela and Toxapex), Toxic (for any walls that want to switch in - though I don't agree with this choice because we have several wall breakers already) and HP Ice (for the Landorus lead if you predict it not to be Choice Scarf - watch out for the uncommon Yache Berry, however).

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Uhoh (Diancie-Mega) @ Diancite
Ability: Magic Bounce
Shiny: Yes
EVs: 4 Atk / 252 SpA / 252 Spe
Hasty Nature
- Hidden Power [Fire]
- Diamond Storm
- Moonblast
- Earth Power

Here is the importable team with my changes

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vegetables (Ferrothorn) @ Leftovers
Ability: Iron Barbs
EVs: 248 HP / 52 Def / 208 SpD
Careful Nature
- Stealth Rock
- Leech Seed
- Power Whip
- Thunder Wave

wingman (Zapdos) @ Leftovers
Ability: Static
Shiny: Yes
EVs: 252 HP / 232 Def / 24 Spe
Bold Nature
IVs: 0 Atk
- Discharge
- Heat Wave
- Hidden Power [Ice]
- Roost

Beefcake (Mamoswine) @ Life Orb
Ability: Thick Fat
EVs: 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- Ice Shard
- Earthquake
- Knock Off
- Icicle Crash

Keldeo-Resolute @ Waterium Z
Ability: Justified
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Hydro Pump
- Taunt
- Calm Mind
- Secret Sword

Tapu Koko @ Choice Scarf
Ability: Electric Surge
EVs: 252 Atk / 64 SpA / 192 Spe
Naive Nature
- Wild Charge
- Volt Switch
- Brave Bird
- Hidden Power [Ice]

Uhoh (Diancie-Mega) @ Diancite
Ability: Magic Bounce
Shiny: Yes
EVs: 4 Atk / 252 SpA / 252 Spe
Hasty Nature
- Hidden Power [Fire]
- Diamond Storm
- Moonblast
- Earth Power

I hope you like the changes. If there are any questions you have, or anything you'd like to discuss further, give me a shout :) Enjoy!