Williams is the only complete RB on their roster in my opinion. If they get rid of him it will be hard for the rest of the backs to fill the hole. Stewart is good but has availability issues. Goodson appears to be a good receiving threat but I'm not sure beyond that. We are all familiar with Sutton. His age doesn't matter to me. The fact that they have a rookie QB is all the more reason to keep him IMO as he needs all the help he can get. If Williams left, and Stewart were to miss a week, would Goodson or Sutton be their starter? That seems like a terrible idea to me.
I would take no less then a first for Williams, and if its a low 1st (as the Packers pick likely will be), perhaps a player as well. If no team bites then I keep him and resign him. Goodson and Sutton are role players at best IMO and the Panther's offense goes through Williams and Stewart, if it's going at all.
With this being said, I'd love to get him. I would be somewhat hesitant to give up a first, but if it was a second and a decent player I'd jump all over it. Great RB and a great attitude which is more than can be said of Marshawn Lynch. If it happened would we keep both Grant and Williams?? I'm not sure. Perhaps Grant would be worth it if he wasn't able to reach many of his incentives.
Either way, I don't see it happening as the Panther's are surely asking too much, and rightfully so.