Humberto Carrillo is a guy who screams “babyface”. Everything about him is loveable, from his look to his moves, his persona, and most importantly, his dimples. You just look at the guy and you want him to win. He even shares the same lineage, being a Mexican like Rey himself. He’s just 24 years old and yet he’s capable of doing amazing things in the ring.
He’s well-versed in the style of Lucha Libre too, and also, him fighting against the world alongside Mysterio on WWE Raw gives a lot of wholesome vibes.
You could argue that his mic skills need work, but that could be fixed by putting him with Dominik and Rey himself. Mysterio could do the talking while Carrillo defends his honor alongside Dominik. They’ll be the most loveable act on Raw while also keeping Mysterio on TV.
Also, you could argue that Dominik himself should take his father’s role, but I think Carrillo is better in the ring and more experienced. WWE could even put the tag belts on Carrillo and Dominik while subtly pushing Carrillo as a singles star, and again, with Carrillo so young right now, we could have a babyface that fans would cheer for years to come.