Flareon has always been the bastard child of the Eevee line since day one, so lets buff him without going crazy or just special snowflaking any buffs to only him as changes usually are wide spread in the game.

1. Change Flare Boost to increase both special and physical attacks by 50% when pokemon is burned or activate if the pokemon is Fire type after using a fire type move, getting hit by one, or is holding a flame orb. Give Flareon this ability. (this is also a buff to Drifblim)

2. Give Flareon, Moltres, Rapidash, Typhlosion, and Magmortar, a new move (with the pretext being you have to attack physically with a body part that has an open flame on it):
Steaming Strike(Physical Fire-type Freeze-Dry essentially):
PP: 20
Power: 70
Acc: 100%
Effect: Has a 10% chance of Burning the target. If used on a Water-type Pokémon, this move ignores the type effectiveness of this move's type against Water and treats it as being super effective against Water types instead

3. New Fire Type status move to Flareon, Entei, Torkoal, Darmanitan, Marowak(AF), Delphox, Rotom(H), Litwick line, Volcanion, Wheezing, Gourgeist, (based on the pretext of purifying a system by fire):
Purifire
PP: 20
Effect: Increases Speed and Special Defense by 1 stage and also removes any and all status' put on the pokemon.

With that do you think Flareon would be more viable? His ability in Flare Boost would give him a woping 190 Attack and 142 Special Attack giving him some insane mixed sweeper potential but still not too broken by his slow speed and minimal move pool. Also with the 2 new moves he would be more versatile in his options as being a heavy hitter who could even hit on water types heavy or even a baton passer.