You may have to do some re-breeding or some replacing with your Pokemon with some of these suggestions, I'm afraid. The vast majority of your team are also not worth using in OU, or are only good as their Mega Evolutions, which you can only have one of in the team.
As tempting as Light Ball Pikachu is, it's not worth using over Electric Pokemon like Wash Rotom and Thundurus. This is because of its frailty comparable to Attack forme Deoxys, as well as its not-bad-but-not-good Speed compared to said Electric Pokemon. Furthermore, it's so dependent on Light Ball that Knock Off ruins it (in fact, the vast majority of Knock Offs KO Pikachu, while the ones that don't make Pikachu significantly weaker by removing its Light Ball).
Wash Rotom:
-Volt Switch
-Hydro Pump
-Will-o-Wisp
-Pain Split/Rest
Nature: Bold
EVs: 252 HP/252 Def/4 SDef
Item: Leftovers/Chesto Berry
Thundurus:
-Thunderbolt
-Hidden Power (Ice)
-Focus Blast/Psychic
-Thunder Wave
Nature: Timid
EVs: 4 Def/252 SAtk/252 Spe
Item: Life Orb/Leftovers
Ability: Prankster
or
-Nasty Plot
-Thunderbolt
-Hidden Power (Ice/Flying)
-Thunder Wave/Substitute/Focus Blast
Nature: Timid
EVs: 4 Def/252 SAtk/252 Spe
Item: Leftovers/Life Orb
Ability: Prankster
or
-Thunderbolt
-Hidden Power (Ice)
-Knock Off
-Superpower/Thunder Wave
Nature: Naive
EVs: 76 Atk/180 SAtk/252 Spe
Item: Life Orb
Ability: Prankster
Charizard X is pretty much the only thing worth keeping, IMO. But Lonely hinders its good Defense, so Jolly is the better option. Also, Flare Blitz is the superior option over Fire Punch for the extra power; the recoil damage can be healed with Roost:
-Dragon Dance
-Flare Blitz
-Dragon Claw
-Roost/Earthquake
Nature: Jolly
EVs: 104 HP/220 Atk/184 Spe (outspeeds Choice Scarf Therian Landorus after a Dragon Dance) or 252 Atk/4 Def/252 Spe
Item: Charizardite X
Ability: Blaze
Blastoise and Venusaur are only good in their Mega Evolved forms. Mega Blastoise is a decent bulky Rapid Spinner that threatens the vast majority of its switch-ins with Mega Launcher-powered attacks, but it lacks reliable recovery. Mega Venusaur has 2 of its weaknesses eliminated with Thick Fat, but you have to pick between that and Charizard. Better alternatives to both are Starmie (which provides Rapid Spin support for Charizard) and Ferrothorn (which can set up Stealth Rock, a very important entry hazard in competitive play):
Starmie:
-Hydro Pump
-Psyshock/Thunderbolt
-Ice Beam/Hidden Power (Fire)
-Rapid Spin
Nature: Timid
EVs: 4 Def/252 SAtk/252 Spe
Item: Life Orb/Leftovers
Ability: Natural Cure/Analytic
or
-Scald
-Psyshock/Reflect Type
-Rapid Spin
-Recover
Nature: Timid
EVs: 248 HP/32 Def/4 SAtk/224 Spe
Item: Leftovers
Ability: Natural Cure
Ferrothorn:
-Stealth Rock/Spikes
-Leech Seed
-Power Whip/Protect
-Gyro Ball/Thunder Wave
Nature: Relaxed
EVs: 252 HP/88 Def/168 SDef
Item: Leftovers/Shed Shell
Ability: Iron Barbs
I'm doubtful about Espeon, but as an offensive Psychic Pokemon, it's outclassed by Mega Medicham, (Mega) Alakazam, Mega Gardevoir, and Mega Gallade, as all four have wider move pools. The best it can do here is act as dual screens support (and Klefki does that better, IMO, since it has Prankster to get its screens up before the opponent does something to it):
-Reflect
-Light Screen
-Psychic/Psyshock
-Baton Pass/Yawn
Nature: Timid
EVs: 252 HP/4 Def/252 Spe
Item: Light Clay
Ability: Magic Bounce
Snorlax, I'm iffy on as well, but it can act as a neat Assault Vest user. While Zen Headbutt hits Fighting Pokemon, Return hits them almost as hard. Retaliate isn't worth using, as it can only be used after an ally has been KOed, and given Snorlax's bad Speed, Snorlax may end up being KOed itself or severely damaged before that happens. Rest also leaves Snorlax a sitting duck for two turns. Snorlax has a wide move pool filled with coverage moves, as outlined below:
-Return/Body Slam
-Fire Punch/Earthquake
-Crunch/Pursuit/Fire Punch
-Self-Destruct/Wild Charge
Nature: Adamant
EVs: 252 Atk/4 Def/252 SDef
Item: Assault Vest
Ability: Thick Fat
Lapras isn't that good, really. While it has good bulk, it's kind of wasted because of its bad defensive typing. If you must use an Ice Pokemon on the team, Mamoswine or Weavile are your best bets, as both have more offensive presence:
Mamoswine:
-Icicle Crash
-Earthquake
-Ice Shard
-Freeze-Dry/Superpower
Nature: Naive/Jolly
EVs: 244 Atk/12 SAtk/252 Spe
Item: Life Orb
Ability: Thick Fat
or
-Stealth Rock
-Ice Shard
-Earthquake
-Endeavor
Nature: Jolly
EVs: 252 Atk/4 Def/252 Spe
Item: Focus Sash
Ability: Thick Fat/Oblivious
Weavile:
-Knock Off
-Icicle Crash
-Ice Shard
-Low Kick/Pursuit/Poison Jab
Nature: Jolly
EVs: 252 Atk/4 Def/252 Spe
Item: Life Orb
Ability: Pressure
