So I looked at this thread and I only saw 2 options, so I'm going to add a 3rd option for light consideration.
Flareon @ Choice Band/Life Orb
Ability: Flash Fire
EVs: 252 Atk / 4 Def / 252 Speed
Adamant Nature
- Flare Blitz
- Superpower
- Quick Attack
- Baton Pass
For our 3rd addition to the team I think we need something that can help make the Leafeon sweep happen more efficiently, and Flareon has some handy tools to make the dream come true.
In my opinion, the biggest thing that makes Flareon an attractive addition to this team is the dry and 'slow' Baton Pass. Flareon will draw in bulky Water, Rock, and Ground types that will more-often-than-not be physically-oriented, so we can use this fact to Baton Pass on the switch and bring Leafeon in on some setup fodder. Switch priority is also a generally handy thing to have, since we do not have a dedicated pivot that can heal itself.
Beyond the dry and slowish Baton Pass, Flareon still has some cool toys to play with. Flare Blitz HURTS off of this set (especially with the Flash Fire bonus) and will soften the opponent's bulky pivots or walls that could stop Leafeon nicely if not outright kill them, giving your opponent a much harder time stopping a Leafeon sweep later. Superpower gives great coverage and can be used if it isn't quite time to bring in Leafeon. Quick Attack is also handy on this team because we are still open to being revenge killed, especially if Piloswine goes down.
The Fire typing and Flash Fire gives us a nice immunity to Will-O-Wisp and adds another redundant layer to the defensive synergy that Piloswine already had going and the Fire STAB gives us great offensive synergy with the Grass, Ice, and Ground STAB we already have. As a final note, Flareon can also be used as a soft check to Ninetales - who is most definitely a problem at the moment - since it has moved away from using Psyshock in favor of Substitute or Dark Pulse.
Overall, I think Flareon is at least worth a thought or 2. This is a long post, but as we get further into teambuilding I feel the need to justify additions more.