Contador is from Madrid. Don't know if you are counting him or not.I looked at the maps and it's clear that Alaphilippe doesn't stand a chance. He's from central France, like, real central. And GT winners from big European countries in these times have to come from the outer parts of a country, close to the coast, like Thomas from Cardiff, Valverde from Murcia, Nibali from Sicily. So obviously Enric Mas will be the next Spanish winner. Benoît Cosnefroy will win the Tour de France. Or Alexys Brunel. But I'm leaning towards Cosnefroy.
For Italy you could say that Ciccone is a good bet then, but have you thought about Pozzovivo...?
My opinion is that Enric Mas is the most likely of the current riders to win his home Grand Tour. One of the big reasons for this is that Movistar specifically does target la Vuelta and always puts a strong team in that race as it is their home race. Yes it would take a few things working in his favor, but I think he has the best chance.