We are talking about competitive battling,right?
Here are my suggestions:
Greninja@Life Orb/Shell Bell
=Ability : Protean=
EVs - HP-4;SpA-252;Speed-252
Nature - Timid(+Speed,-Attack)
-Hydro Pump
-Ice Beam
-Dark Pulse
-Extrasensory
Manectric@Manectite
=Ability : Lightningrod=
EVs - Att-4;SpA-252;Speed-252
Nature-Hasty(+Speed,-Def)
-Flamethrower
-Volt Switch
-Discharge
-Ice Fang
Forretress@Occa Berry(Lowers Damage from Fire type attacks)
=Ability : Sturdy=
EVs - HP-120;Att-44;Def-172;SpDef-172
Nature:Imprish(+Def,-SpA)
or
Nature:Careful(+SpDef,-SpA)
-Spikes
-Toxic Spikes
-Stealth Rock
-Earthquake
Espeon@Leftovers
=Ability : Magic Bounce=
EVs - HP-4;SpA-252;Speed-252
Nature-Timid(+Speed,-Att)
-Calm Mind
-Psychic
-Shadow Ball
-Baton Pass
Charizard@Charizardite Y
=Ability : Blaze/Drought while Mega Charizard Y)
EVs - HP-4;SpA-252;Speed-252
Nature-Timid(+Speed,-Att)
-Dragon Pulse
-Solarbeam
-Flamethrower/Heat Wave/Fire Blast
-Tailwind/Air Slash
Gengar@Black Sludge
=Ability : Levitate=
EVs - Att-4;SpA-252;Speed-252
Nature-Hasty(+Speed,-Def)
-Shadow Ball
-Sludge Bomb/Wave
-Brick Break
-Destiny Bond
Shell Bell doesn't do much for Greninja because it's too frail to make use of any passive recovery. The HP restored by Shell Bell is too minuscule to be even worth using and Greninja needs the extra power from Life Orb.
While Ice Fang theoretically fills in HP Ice's moveslot, it runs off of Mega Manectric's lower Attack stat. HP Ice is mandatory on Mega Manectric so it can deal with Dragons. Overheat is also mandatory over Flamethrower for the raw power alone. Mega Manectric is too frail to make use of Discharge's paralysis rate, so Thunderbolt is the generally better option.
Forretress is bait for Aegislash; it can come in freely, whether to block Rapid Spin or on a move not named Earthquake and threaten it out with Shadow Ball. It's difficult for Forretress to hazard-stack this time around because of Defog everywhere.
Espeon's niche as a Baton Passer is no more because of the Baton Pass nerf to 1 Baton Passing member per team. Even then, Espeon is too frail to Calm Mind up, IMO.
There's no reason for Charizard Y to use Air Slash, when sun-boosted Flamethrowers and Fire Blasts inflict more damage on Air Slash's targets:
252 SpA Mega Charizard Y Fire Blast vs. 0 HP / 236 SpD Assault Vest Conkeldurr in Sun: 220-261 (62.6 - 74.3%) -- guaranteed 2HKO
252 SpA Mega Charizard Y Air Slash vs. 0 HP / 236 SpD Assault Vest Conkeldurr: 200-236 (56.9 - 67.2%) -- guaranteed 2HKO
A physical move on Gengar is a seriously bad idea. Its Attack is significantly lower than its Special Attack. If you want a Fighting move on Gengar, use Focus Blast, no matter how off-putting the accuracy is.
