To start off, I'm not very well read in terms of Westerns. I've seen a few. The usual John Wayne ones that show on a Sunday afternoons on those satellite channels that no one knows they actually subscribed to. Firefly, is a sort of Sci-Fi Western. But not much in terms of books.
I read Redeeming Love which is a retelling of a story from the book of Hosea in the Bible. However, its set in the California Gold Rush and has that very rustic Western feel.
There is also Rumours, the second book in the Luxe Series briefly has two of the characters out West.
But other than that I'm fairly limited. Although I enjoy the premise, it doesn't seem to go anywhere. It's very much a rinse and repeat. Look for a new start out west, have a long hard journey to get there, maybe battle a few Native American Indians along the way, bobs your Uncle, you have yourself a Western.
But I suppose that's the same with every genre after a while. I mean, European historical tends to get a bit samey after a while too. I guess it's just how you make your story different that will set you apart from the soup of your competitors.
If I was to ever tackle the Western genre (never say never) I think I might mash it up with something else. But not sci-fi. That's Firefly territory, and Firefly fans are quite... protective of their fandom. I should know, I am one.
Have you read many Western books?