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If I recall in LGPE, non-kanto mons still have placeholder data in the games, but they're buggy, use a marowak model/animations, and have no moves. They, however, still have their typing and stats.
By this logic, there's a chance that all cut pokemons still have a data entry in SwSh and all they need are their models, animations, movesets, and a few more tweaks to prevent them from crashing the game.
However that being said, without the source code, people would need to first find a way to hack it to create a pokemon editor to make these changes. Do you also think there's gonna be a modders devoted enough to put all the effort into import 100(?)+ pokemons? It'd need to be open-source collab project to get it completed without having some lone modder going insane.