Hi False Sense & Gary2346
This is a very solid team with the suggestions you have had so I only have these switches. Change Skarmory's EVs to Specially Defensive 252 HP / 4 Atk / 252 SDef
with Calm Nature
. Wobbefut is so uncommon, you can get the extra bulk to avoid some special 2HKOs instead of wasting valuable EVs. This will make switching into Draco Meteors much easier. Mamoswine is the biggest threat to this team at the moment as the combo of Ice Shard + Stone Edge + Earthquake + Icicle Crash will plow through this teams core and is even a bigger threat as this set will be used 90% of the time. Gyarados willl be easily killed even though it resists EQ and will be fainted by a Icicle Crash because of SR. Skarmory is very valuable and is a solid member of this team. Latios needs to be at full health so I am not giving a suggestion, but be aware of the mammoth. Anyways I also recommend Heatran
over Skarmory. Sun teams are a major threat to this team. TNT and Intergalactic are right.
Heatran @ Leftovers
252 HP / 252 SDef / 4 Spe
0 Atk IVs
Stealth Rock | Roar | Lava Plume | Protect
Celebi can run Perish Song
or Healing Wish
with the empty slot now. Great team!