You have an alright start, but some things can be optimized, some not used altogether. I'd say give the following a try:
Tapu Lele @ Psychium Z
Ability: Psychic Surge
Level: 50
EVs: 4 HP / 252 SpA / 252 Spe
Timid Nature
IVs: 0 Atk
- Moonblast
- Protect
- Psychic
- Energy Ball
Psychium Z is really the best item for Tapu Lele. Shattered Psyche under Psychic Terrain is just massive damage and is usually enough to OHKO just about any threat. Moonblast for STAB and it's gonna hurt Garchomp pretty bad and Energy Ball because.
Pheromosa @ Choice Band
Ability: Beast Boost
Level: 50
EVs: 252 Atk / 4 SpA / 252 Spe
Lonely Nature
- High Jump Kick
- U-turn
- Poison Jab
- Ice Beam
I've never used Pheromosa, but you wanted it so I left it, however, at 151 base speed (highest base speed in VGC17) there's not really a reason to go for speed over damage with your nature so try and get a Lonely one.
Mimikyu @ Ghostium Z
Ability: Disguise
Level: 50
EVs: 4 HP / 252 Atk / 252 Spe
Jolly Nature
- Swords Dance
- Shadow Claw
- Wood Hammer
- Play Rough
Shadow Claw does more damage than Shadow Sneak and with Ghostium Z you OHKO Tapu Lele 100%. Jolly Mimikyu outspeeds non-scarfed Timid Lele by 1 point as well.
Marowak-Alola @ Thick Club
Ability: Lightning Rod
EVs: 116 HP / 140 Atk / 252 Spe
Adamant Nature
- Flare Blitz
- Shadow Bone
- Protect
- Will-O-Wisp
I personally used this exact Marowak for the longest time. 140 Att with Thick Club OHKOs Celesteela 100% of the time. Bonemerang isn't the greatest move as it doesn't typically OHKO anything so for the third moveslot I like to run Will-O-Wisp.
Tapu Koko @ Life Orb
Ability: Electric Surge
EVs: 4 HP / 252 SpA / 252 Spe
Modest Nature
IVs: 0 Atk
- Thunderbolt
- Hidden Power [Ice]
- Protect
- Taunt
When in doubt, put in Tapu Koko. This particular set will OHKO the standard Z Crystal Garchomp with HP Ice, as well as Celesteela with Thunderbolt. Taunt for Eevee/TR disruption.
Celesteela @ Leftovers
Ability: Beast Boost
Level: 50
EVs: 252 HP / 252 Atk / 4 SpA
Brave Nature
- Flamethrower
- Heavy Slam
- Leech Seed
- Protect
This is another one I just sorta guessed at. Celesteela is already slow so being slower doesn't hurt. Flamethrower will OHKO Kartana and Leech Seed and Protect will allow you to be really annoying and put that HP to use.
Feel free to totally disregard any or all of this if you'd like. This is just what I would do to your team. I haven't done any Showdown testing with this though so I might even change some things like get rid of Mimikyu, add Kartana, get rid of Marowak, add Arcanine.
Team in spoiler to easily copy and paste into Showdown.
Tapu Lele @ Psychium Z
Ability: Psychic Surge
Level: 50
EVs: 4 HP / 252 SpA / 252 Spe
Timid Nature
IVs: 0 Atk
- Moonblast
- Protect
- Psychic
- Energy Ball
Psychium Z is really the best item for Tapu Lele. Shattered Psyche under Psychic Terrain is just massive damage and is usually enough to OHKO just about any threat. Moonblast for STAB and it's gonna hurt Garchomp pretty bad and Energy Ball because.
Pheromosa @ Choice Band
Ability: Beast Boost
Level: 50
EVs: 252 Atk / 4 SpA / 252 Spe
Lonely Nature
- High Jump Kick
- U-turn
- Poison Jab
- Ice Beam
I've never used Pheromosa, but you wanted it so I left it, however, at 151 base speed (highest base speed in VGC17) there's not really a reason to go for speed over damage with your nature so try and get a Lonely one.
Mimikyu @ Ghostium Z
Ability: Disguise
Level: 50
EVs: 4 HP / 252 Atk / 252 Spe
Jolly Nature
- Swords Dance
- Shadow Claw
- Wood Hammer
- Play Rough
Shadow Claw does more damage than Shadow Sneak and with Ghostium Z you OHKO Tapu Lele 100%. Jolly Mimikyu outspeeds non-scarfed Timid Lele by 1 point as well.
Marowak-Alola @ Thick Club
Ability: Lightning Rod
EVs: 116 HP / 140 Atk / 252 Spe
Adamant Nature
- Flare Blitz
- Shadow Bone
- Protect
- Will-O-Wisp
I personally used this exact Marowak for the longest time. 140 Att with Thick Club OHKOs Celesteela 100% of the time. Bonemerang isn't the greatest move as it doesn't typically OHKO anything so for the third moveslot I like to run Will-O-Wisp.
Tapu Koko @ Life Orb
Ability: Electric Surge
EVs: 4 HP / 252 SpA / 252 Spe
Modest Nature
IVs: 0 Atk
- Thunderbolt
- Hidden Power [Ice]
- Protect
- Taunt
When in doubt, put in Tapu Koko. This particular set will OHKO the standard Z Crystal Garchomp with HP Ice, as well as Celesteela with Thunderbolt. Taunt for Eevee/TR disruption.
Celesteela @ Leftovers
Ability: Beast Boost
Level: 50
EVs: 252 HP / 252 Atk / 4 SpA
Brave Nature
- Flamethrower
- Heavy Slam
- Leech Seed
- Protect
This is another one I just sorta guessed at. Celesteela is already slow so being slower doesn't hurt. Flamethrower will OHKO Kartana and Leech Seed and Protect will allow you to be really annoying and put that HP to use.
Feel free to totally disregard any or all of this if you'd like. This is just what I would do to your team. I haven't done any Showdown testing with this though so I might even change some things like get rid of Mimikyu, add Kartana, get rid of Marowak, add Arcanine.
Team in spoiler to easily copy and paste into Showdown.
Just a fossil from the days of olde.
Sword and Shield Trades
Sword and Shield Trades
