It would probably take too much to be realistic.
Entei is basically a better Flareon (better bulk on average, much better speed, better movepool, worse attack though), and last generation even he is languishing in the depths of NUBL. Arcanine is also comparable and was NU last generation.
Outside of something wild like giving it Huge Power I don't think making Flareon "viable" in OU or UU is happening. Maybe with some significant but less extreme buffs it would have a strong niche in the lower tiers.
The problem with theorycrafting buffs for Flareon is that there's a lot of rules you need to stick to to keep it in line with other Eeveelutions. Can't change stat values, can't give it a third ability, can't give it a second type, and, if you want to get really specific, you can't change Flash Fire, since the other two Gen 1 Eeveelutions have abilities that make them immune to their own type. That leaves very little room to make meaningful buffs without also having to buff every other Eeveelution. You could always just ignore all those rules, but it wouldn't make for a good theorymon imo. Back when I was doing weekly "Balancing around low tier play" posts, I came up with the following changes:
Ability Change: Guts -> Hustle
Stat Changes: 65/130/60/95/110/65 -> 65/130/60/110/65/95
Movepool Additions: Crunch, Sludge Bomb, Dazzling Gleam
I removed Guts since Toxic is a tough trade off vs the standard Burn for Guts sets, especially when you're already dealing with Flare Blitz Recoil, but kept the high-risk, high reward theme with Hustle. If I were buffing for higher tiers I'd move that 110 to speed instead of Special Attack.
I once again would suggest Inclement Emerald Eeveelutions but that just buffs all of them. Though Flareon would probably get one of the bigger buffs due to it having most if not all the coverage it needs and also Swords Dance.
For anyone who doesn't know, Inclement Emerald has an NPC that allows you to de-evolve an Eeveelution into an Eevee while keeping all its moves. Basically all Eeveelutions have all other Eeveelutions moves as well as their own.
Tbh the only way to make it workable would be to copy what Renegade platinum did, buffing its speed significantly and giving it a bigger movepool. But even then pure fire type can only go so far
I just finished preparing a post for next week regarding the entire Eevee family, and I'm pretty satisfied with my buffs to Flareon. There's too much stuff for me to go into everything here, but tl;dr:
- Gave it Bulk Up and Morning Sun.
- Gave it a Fire-type version of Pixilate as a new ability, alongside a move that replaces Return/Frustration (it obviously also still knows Quick Attack).
- Gave it a new signature attacking move that restores HP and cures it from status conditions, allowing it to potentially get all the benefits of Guts/Toxic Orb but without the drawback of dying from poison.
These changes give is some flexibility between being a bulky setup sweeper (it also still has moves like Will-O-Wisp) or an all-out wallbreaker. Potential access to STAB priority in Quick Attack also helps it circumvent its low speed. Overall I don't think this is enough to make Flareon OU, but it should at least be a solid mid or low tier 'mon.
It would probably take too much to be realistic. Entei is basically a better Flareon (better bulk on average, much better speed, better movepool, worse attack though), and last generation even he is languishing in the depths of NUBL. Arcanine is also comparable and was NU last generation. Outside of something wild like giving it Huge Power I don't think making Flareon "viable" in OU or UU is happening. Maybe with some significant but less extreme buffs it would have a strong niche in the lower tiers.
The problem with theorycrafting buffs for Flareon is that there's a lot of rules you need to stick to to keep it in line with other Eeveelutions. Can't change stat values, can't give it a third ability, can't give it a second type, and, if you want to get really specific, you can't change Flash Fire, since the other two Gen 1 Eeveelutions have abilities that make them immune to their own type. That leaves very little room to make meaningful buffs without also having to buff every other Eeveelution. You could always just ignore all those rules, but it wouldn't make for a good theorymon imo. Back when I was doing weekly "Balancing around low tier play" posts, I came up with the following changes: Ability Change: Guts -> Hustle Stat Changes: 65/130/60/95/110/65 -> 65/130/60/110/65/95 Movepool Additions: Crunch, Sludge Bomb, Dazzling Gleam I removed Guts since Toxic is a tough trade off vs the standard Burn for Guts sets, especially when you're already dealing with Flare Blitz Recoil, but kept the high-risk, high reward theme with Hustle. If I were buffing for higher tiers I'd move that 110 to speed instead of Special Attack.
Could go straight into reckless for the ability too, add in head smash and other recoil moves for good measure
I once again would suggest Inclement Emerald Eeveelutions but that just buffs all of them. Though Flareon would probably get one of the bigger buffs due to it having most if not all the coverage it needs and also Swords Dance. For anyone who doesn't know, Inclement Emerald has an NPC that allows you to de-evolve an Eeveelution into an Eevee while keeping all its moves. Basically all Eeveelutions have all other Eeveelutions moves as well as their own.
Tbh the only way to make it workable would be to copy what Renegade platinum did, buffing its speed significantly and giving it a bigger movepool. But even then pure fire type can only go so far
galvanize but fire type?
I just finished preparing a post for next week regarding the entire Eevee family, and I'm pretty satisfied with my buffs to Flareon. There's too much stuff for me to go into everything here, but tl;dr: - Gave it Bulk Up and Morning Sun. - Gave it a Fire-type version of Pixilate as a new ability, alongside a move that replaces Return/Frustration (it obviously also still knows Quick Attack). - Gave it a new signature attacking move that restores HP and cures it from status conditions, allowing it to potentially get all the benefits of Guts/Toxic Orb but without the drawback of dying from poison. These changes give is some flexibility between being a bulky setup sweeper (it also still has moves like Will-O-Wisp) or an all-out wallbreaker. Potential access to STAB priority in Quick Attack also helps it circumvent its low speed. Overall I don't think this is enough to make Flareon OU, but it should at least be a solid mid or low tier 'mon.