Rafa is playing pretty well, to be fair. He's serving really well, but the blips he has had have all notably come at the tail end of sets (in the breakers with Thiem, serving last in the second with Tsitsipas).
I agree that with the exception of Thiem the other three matches all look winnable. Zverev looks pretty bad, and Novak got bossed by Medvedev, but you know both those guys can turn it on against him.
Medvedev as Bercy champion, and being 2 for 2 here is pretty much the form player and after last year will surely want vengeance here too. As far as Thiem is concerned, their matches this year have all basically come down to tiebreakers, yeah, but I don't think you can dismiss it as luck when he's won all 5 of them
I think Nadal's best chance there is assuming Domi continues to be a massive choke artist in finals.
I agree it's as good a chance as he's going to get being relatively fresh after the short year, in good form, with nobody looking particularly dominant and as he's only going to get older and older each time after, but... I dunno, I'd give him a 50/50 chance, I don't know that it's much better than that. Today's early match will be telling.