I think when it comes to Toad playable characters, outside the glaring omission of Toadsworth I don't necessarily need further Toad characters to have their own slots on rosters. Would be nice to have, but in the grand scheme of things I think the characters wholly original to the RPGs would be the most appealing representatives for them, the ones whose entire species was introduced in those games.
Toad (or Captain Toad), Toadette and Toadsworth are suitable to be the main members of the species on playable rosters. Otherwise I think I just want generic female Toads and more preset design variants appearing as NPCs, including in audiences for Kart and Sports games, and more distinct individualized designs used when they put Toads in specific roles, like shopkeeper, innkeeper, mystic, banker, cook etc. This is also a great place to bring back past distinct Toad designs like Toadbert, Tayce T., or Dr. Toadley (though in the latter's case I also want the Merlon clan to have a stronger presence so I'd prefer an approach that allows them to coexist despite overlapping a bit in theming)
If they're playing a more distinct role than just filling space in the background their design absolutely shouldn't default to the standard one, but the space fillers should still include female Toads, and some variety in accessories and facial hair would be nice too. Nothing entirely individualized, but just more preset designs to sprinkle in than "colors of the regular design."
Basically, a new model sheet for background Toads that includes different hairstyle options, facial hair options, and accessories like glasses and a handful of basic outfits. Rather than just "here's the basic Toad design in different colors duplicated a lot"