There are really only a few guys that I'd be interested in right now, and all three of them are long shots who have some type of mystery or ailment surrounding them. That said, for the right price any of the three could contribute to the 2015 squad.
OL---Jake Long
OL---Evan Mathis
DL---Red Bryant
I read a piece on NEPatriotsdraft.com where it was talking about a possible surprise, Belichick veteran trade candidate being Sebastian Vollmer. If this were the case, I think Jake long would be a good insurance policy.
I would love to have Mathis, I think everyone would. He would be perfect to have while we groom our 2 new guards. Obviously it would have to be at the right price. I wouldn't want him if it affected our ability to re-sign Hightower and possibly Jones. I do think it would greatly help us in our division, and also at a shot at repeating.
As far as running backs go, I would love to have Ahmad Bradshaw. If he could stay healthy, he would easily be the best overall back on our team. I think with the way we use a RBBC approach, he would make a great fit for the team, he might just be able to stay healthy for once. I still can't believe he hasn't been signed by a team yet, when healthy, he is easily a top 15 back in this league. To me, that upside alone makes him a good candidate.
For WR's, I wouldn't mind seeing James Jones get a shot. I still think he has a little left in the tank, and could still put up Lafell like numbers if reunited with an elite QB like his time in GB. He didn't have a really bad year last year on the raiders despite being their #1 WR, which at this point in his career he is much better suited as a #2. If either Edelman or Lafell were to go down at any point in the season, I think he would probably fill in fairly nicely.
My last dark horse is Colt Lyerla. Ive always had a pipe dream of the team giving him a shot, and pairing him up with Gronk. I know he's had his issues, but the mistakes he made aren't on the level where I don't think he deserves at least one more shot in the NFL. I read a article where he said he's been training and plans on giving the NFL one more shot this coming season. His athletic upside and versatility alone, make him a candidate for the Practice squad. Give the man a chance!