>>55486926BUT if I'm wrong, let's so some process of elimination.
>Gen 6Out because the game is in Kalos, and they'd be rare encounters in game.
>Gens 1 and 3Out because, again Mega Evolutions are returning. Why make regional forms when they have Megas that you could just bring back instead?
>Gen 9Too recent/new. Really doubt they'd get new forms already. Maybe in Gen 10.
This leaves Gens 2, 4, 5, 7, and 8
Of those Gens, two of them have starters already related to France: Gen 4's Piplup and Gen 5's Snivy
Leaving us with just the Fire starters, which means we can rule out Gen 2 since we already got Hisuian Typhlosion.
So
>Snivy>Either Litten or Scorbunny>PiplupAnd this is assuming they'd be willing to repeat (Two Gen 5 Pokemon in a row get Regionals, leaving one out)
Only solution then would be going with Scorbunny and replacing Snivy with Sprigatito, ignoring the Gen 9 rule-out.