I think that in order to not have a crush on Cap, you have to be absolutely and 100% not attracted to men. He's the Marvel U's Exception that way. I can totally see Billy having a mad crush on Cap. And Cap, of course, is monogamous with Tony/wouldn't go after jailbait, but that just MAKES THE CRUSH WORSE, because what's not to want about a guy who's too honorable to take advantage of you even when you want to be taken advantage of plz.