First off, comparing what the Patriots had to give up to get Moss and Welker with what we would most likely have to give up for Williams is stuipd. Moss is considerably older and has had quite a few "issues" over his career. And, who out there thought Welker was as good as he has been this year? Nobody, that's who. Prior to this year, he was just a quick little slot receiver.
Here's what I'd be willing to do.
1) Trade either of our # 1s (not both) and a # 2 or a # 3 for Fitzgerald. Not going to happen, but I'd do it in a heartbeat.
2) Trade our 28th and a 6th or 7th for Roy Williams. I wouldn't trade a # 1 AND a # 2. Might even consider a # 3, but not # 2.
We're just a piece or two away from being the most talented (and young) team in the entire league. We have to draft a top notch CB in the draft. We also have to either draft or sign a fast RB to compliment Barber. Given that we probably can't make a trade for Fitzgerald, I'd certainly settle for this. Draft the best CB available at # 22. Trade our # 28 to Detroit and get Williams. Draft one of the many very good RBs with our 2nd round pick. Very few rookies are going to make our team next year. We really don't have much of a need to keep 6th and 7th round picks. Use them to trade up for fewer higher rated picks. As an alternative, we could sign a FA running back like Turner, but what will he cost? The bottom line is this. We HAVE to get a good, young, and fast WR and CB, along with a speedy RB this off-season, through both FA and the draft. Everything else is just gravy.