My number one villager I would like to see return is Pigleg. His concept is cool, I like the design and I feel like he would fit the deserted island setting of New Horizons well.
After that it's kind of messy.
If it were somehow possible and there weren't any licensing issues or whatever, considering they were from a different Japanese company's products back in 2002, I would love to see Bow and Meow return. Reason being, I love all of the robot villagers in the series and would like to see a robot villager for all of the species someday, so these villagers with digital screens for faces would be cool twists on the concept. Additionally, their faces being digital screens, they could have neat, unique facial expressions show up on their screens that you can't do with villagers that have actual, physical facial structure.
That said, since I don't think Bow and Meow will ever return (not that this hypothetical is going to happen in this game either, but hey) the other two who I would like to see return are Pierre and one of either Aziz or Elina. I was bummed that Pierre didn't return back in New Leaf's Welcome Amiibo update considering one of my New Leaf towns is a circus and magic show themed town and he would've fit in well, and I just generally like clown aesthetics, so I'd like to see him make his return.
As for Aziz or Elina, I always thought Aziz looked cool in the GameCube game's guidebook, but I never had the opportunity to have him in my town so it would be cool to see him return. Meanwhile, I like Elina's design with the bindi and the lotus flower in her hair. That said, considering Leigh and Quetzal probably aren't returning, I doubt Elina will either, and I understand it and am cool with it. I would see Aziz's return as more likely considering Elina's name in Japanese is lazily just Bindi, so even if they remove the bindi from her model like they did in the international release of the GameCube game, probably not the best look in 2023. A shame though, because as someone who loves villagers to have unique features, I'd love to see her with the lotus flower hair accessory in the modern graphics. Aziz also had a purple bindi in the Japanese version that wasn't featured internationally, but it's not as inextricably linked to his design as it is to Elina's, so he's otherwise just a lion with a cool blue mane that could fit seamlessly back into the franchise.