Thing is, even if you look at all the Mario Kart characters, there's only a handful that are big names. Nobody wants to play as a Shy Guy. Even Link and Zelda feel wildly out of place, although maybe they wouldn't have done in a Links Awakening style rather than what they went for.

I think Sony could do an Astro Bot on it and put in a bunch of their other characters in there. Lego has potential if they can get a bunch of their licensed characters in there (although you know with that kind of money floating around, most of them will be DLC locked behind Harry Potter packs, etc). A horrendously expensive MCU license maybe with some chibified characters.

I think Mario Kart just has that easy "an idiot can play it" gameplay, but it doesn't get boring once you know what you're doing. It's a really hard balance to get right. The only recent attempt was CTR, and it didn't have that first factor at all, it was hard as nails.