If you can get Nomar (or, theoretically, Jeter) for Vazquez, I'd go for it. Try adding Cabrera to the deal to improve your chances - I don't think most folks would agree to a one-for-one.
I don't think you need to pursue LoDuca, though. A Hall/Fick combo is pretty good already.
I honestly don't know about Nunez. He'll get the chance to show his stuff now, but it remains to be seen if he has a closer's makeup. Looper, though ineffective so far, can't be completely ruled out yet, and Neal is waiting in the wings. Still, any player who'll get saves is worthwhile - just don't expect too much too quickly.