I agree, Smith has played well at WR over the past two games, and i think Chan will keep him there for the remainder of the season. He's got more speed on the outside than Naaman(who shouldn't be starting anyways), and Nelson belongs in the slot. As long as Smith continues to make plays, I think he's the one who belongs opposite of Stevie.
With that established, we're left with only Thigpen backing up Fitz, who has done nothing to show he's capable of running the offense effectively, let alone winning any games. Harrell had a stellar college career, and at this point nobody knows what his future in the NFL will be. Why not try bringing him in and seeing what he's got?