Hanley doesn't want to play SS anymore as far as I remember. Holt would be a serviceable replacement, but he's not a starter. I honestly think he played a little over his head last season and could regress. He's definitely an off the bench utility guy.
I think we sign Shields and call it a day, if he can be had for a reasonable contract, that might be the best move really. As much as I'd like to see Hamels in a sox uni, I think trading for him will simply cost too much.