I would certainly so "no" to Jones. We have 5 solid DT's without Jones or Thornton. 5 DT's are plenty, especially give that Grissom and Chandler Jones sometimes takes reps inside. Besides, Chris Jones can stay on IR and be given a chance agains next year.
Fletcher is a more complicated matter. How healthy is Hightower? Mayo doesn't look good. Bostic still doesn't have one rep as a linebacker. So, with regard to Fletcher, I would think that we might wait a couple of weeks, and ultimately decide based on the the health of everyone else. To me, Fletcher would be an OK 5th LB, who plays ST's, but Bostic may have already replaced him.