No, Williams is too inconsistent. Has been his whole career, which is why he is on his 3rd team.
He's not actually that inconsistent. He had a bad year last year but prior to that, 3 straight years of double digit sacks. He did quit last year on the Bills and have a bad season but he wasn't the only one. That entire team kind of bailed on the season, especially the defense. He signed a deal that basically allows Miami to cut him after this season for little pain at all.
And again here's the reality. Other than possibly Lawrence, who is likely out for four games, there isn't another player on this roster that's even close to him in terms of talent at DE. Note, I am not saying he's the guy from 7 years go. But he's better than just about every other DE we have on this roster other than a guy who might be suspended for drugs and is coming off back surgery.
Anyone seriously believing that a guy like James Jones or Adrian Clayborn or whatever other bargain bin DEs the Cowboys looked at improve this team more than Williams would have is really drinking the front office kool aid IMO.