>>51473131I'd genuinely have loved if breeding certain species together would've always resulted in a hybrid species. Like there'd be certain Pokémon family lines you just couldn't find in the wild, you'd have to breed them. And they'd be hybrids look-wise, stat-wise and their movepools would also be a mix. There shouldn't have to bee tons of these pokémon, but let's say they added like ten or so every generation. Like maybe a hybrid for every starter line together with some similar or compatible Pokémon from their gen. Mayve Feraligatr and Tyranitar WOULD result in a Water/Dark type hybrid line. Maybe Meganium could breed with Ampharos to create a Grass/Electric hybrid that's a mix of them both. Maybe Typhlosion could breed with Granbull to make a Fire/Fairy type abomination. And every gen could also add a few ones that could create hybrids with old Pokémon, too. It'd have been a gimmick not unlike regional Pokémon; a way to indirectly give relevance to an old Pokémon. You might not care of some shitter like Dunsparce, but if it was REALLY hard to find one and you could breed it with Castform to create some super weird weather dragon, you'd suddenly be a bit interested.
(Disclaimer: I actually love Dunsparce)