There could definitely be a story there, one I could explore in great depth, one which takes place after this one, when Lucas and Jubal are settled.
We don't know a lot about Billy, other than he appears to have some hero worship for Reid... and if he is gay, Reid would certainly be a man he would be attracted to. Interesting about Billy being effeminate. I'm not sure he is... it doesn't seem he is speculated about, except by us, but he could well be, though he hides it. And I see where he might be considered softer. He does seem quieter, but maybe because we haven't seen enough of him. You're right that we do know he had some sort of troubled past... maybe we'll find out more... or not.
Oh man, do I ever agree about secondary characters and their importance. Think about Sheriff Willard, Old Man Corker, Alan Bright, Phineas Lemon, and Will Merrick from Sidewinder. They all made the story better, and even Wes, Lee, Dan, and Will, the evil Sidewinder himself, all of who we didn't ever meet, were major contributors to the story. This author knows their importance to what he does, and I appreciate you making the point. I mean, after all, two of those side characters had their own story eventually... with Larkspur.