The presence of Walt Goggins as part of the cast made me think that whoever is doing casting for the show probably remembered that "Deadwood" was successful largely on the basis of Ian McShane being cast as Olyphant's co-star, with the actor pretty much carrying the show for it's three short seasons. But him not being a series regular does fill me with dread, unless they plan on his character existing within the background of the series and not in every episode.
I think the protagonist here may be more straightforwardly heroic than the "hero" of The Shield.
Which means that they'll need to find something to hook viewers if they are simply giving us generic a generic anti-hero as a protagonist. FX has largely made it's back off of shows that explore and deconstruct the formula of the anti-hero, meaning that the writers are going to need to come up with some sort of angle to make the character interesting and not just be a neutered, non-threatening, safe for kids version of Vic Mackey for the show to have legs.
Like his Sheriff Bullock on Deadwood or in High Life from last year. Bullock would look rather boring on paper or in a promo clip but the character was one of the most layered creations I've seen on TV. Good writing of course helps.
He had Ian McShane to help him, not just good writing. Olyphant is one of those actors who is is only as good as whoever he's playing off of and having writers who understand his limitations and working around them. And in the case of Deadwood, the writers quickly realized that Swearengen was the more interesting character and wrote the character of Bullock to play off the character in that regard.
Which is why I think that the casting of Goggins is good for the series and why I am hoping they'll find a way to keep him around, since Goggins could make for an excellent foil for Olyphant IMHO.