Of course, if this news is true, the film will have Smith doing his wimp-ass grin the whole way through and have as soundtrack the requisite rap crap. And I bet they'll even fit in Will's old standby: "Oh, hell, no!"
Clint's very presence screams, Don't mess with me. I am not one to be fucked with.
Will is a hammy jokester who is about as intimidating/authoritative as a meatball.
(P.S. I, too, have always marvelled at how similar Hugh is in appearance to a young Clint.)