I thought the issue (or one of the issues) with Christie was that he put Jared Kushner's dad in jail and that's why he didn't get a White House job. If Sessions resigns and Trump recess-appoints Christie, the Senate can do confirmation hearings "when they get around to it" (which could be never) so the expected confirmation nastiness might not ever need to happen.
Also, no possibility of a fistfight between Christie and Kushner because Christie would be at DOJ, not the WH. He might be unpopular in some circles if he fires Mueller -- but I think that since Bridgegate and since Beachgate Christie actually enjoys all the hate.
Recess-appointing Giuliani would probably be smoother -- although I don't know if he would want the job. He may have some health issues.
I would love to see Gowdy in the AG position. Although he has been in mostly toothless hearings, in a position to act, I believe he would. He certainly comes in armed with the facts. I do doubt that he would accept it, however.