I just checked and another 2-stage line with the same BST as Rapidash are Donovan and Mudsdale.
As the latter is a very recent one I am counting out a Galarian form for it.
Donphan on the other hand...
Mudsdale has the same BST as Rapidash?! But its so much better! Man, that just makes me feel sadder for Rapidash. It's such a cool pokemon, but it always seemed so underwhelming. Maybe because everything was split so awkwardly and it never really had access to the greatest movepool.
Now, with a Psychic typing though, it should have access to a LOT more. Psychic, Normal, and Ghost types seem to be the gateway to almost every other typed move available for whatever reason. Learning elemental moves of another type is so much harder if you're not one of those (unless you're in the Rhyhorn family for some odd reason).
Aside from hopefully benefiting from new moves added this generation in general, Rapidash should get access to things like Zen Headbutt and Mirror Coat which should really help its outlook.
As far as Mudsdale and Donovan go, I feel like Mudsdale is a bit too new to already get a new form. And we already have vague proof of an elephant pokemon of some kind already. Whether its a regional variant to Donovan or an evolution to Polteageist may still be up in the air, I kinda hope its Polteageist. Donovan's cool and all, but I really want that teapot to be a 3 formed pokemon lol.
*Translater's note: Keikaku means plan. Also Donovan = Donphan*