Heatran @ Choice Specs
Ability: Flash Fire
EVs: 252 HP / 4 HP / 252 SpA
Modest Nature
- Fire Blast
- Earth Power
- Flash Cannon
- Hidden Power [Electric] / Hidden Power [Grass]
or Heatran @ Choice Scarf
Ability: Flash Fire
EVs: 252 SpA / 252 Spe / 4 HP
Timid / Modest Nature
- Eruption
- Flash Cannon
- Earth Power
- Overheat / Lava Plume
Charizard-Mega-Y @ Charizardite Y
Ability: Blaze --> Drought
EVs: 252 SpA / 252 Spe / 4 Def
Timid Nature
- Fire Blast
- Solar Beam
- Focus Blast
- Hidden Power [Electric] / Air Slash
Since 2 team members are weak to Fire and the resists are rather frail, Heatran can be a paramount switch-in. It can also thwart things like Volcarona and frees up a Mega slot. However, that would make 3 of my team members weak to Ground. Charizard Y requires Defog support but it can shut down rain teams and hit Pelipper coming in to set rain back up with HP Electric. I don't know which one I should choose, they both have their pros and cons.