I'd favor Hagler over Jones 60/40 at 160, because I think Marvin would be able to get into Roy's chest and keep him against the ropes, something Roy was prone to doing even then. I'd probably go 70/30 in a 15-round fight. At 168, Roy would be too big for Marvin. There's no one in history I'd favor against him there. Griffin gave Jones problems (but they are overstated, as Roy figured him out) because of the unorthodox movement fighting out of a crouch. Jones matches up extremely well with Calzaghe, and I think an 8-4 loss is as well as Joe possibly could hope to do. Tough to say on Robinson. Different era.
I don't see Hearns doing anything Jones at 160. His chin wouldn't hold up. Also, no fighter who made Jones come forward ever had any success at all. He's the worst possible matchup for a counterpuncher. I agree that an aggressive guy like Hagler would have a good shot.
Cant hurt what you cant hit. RJJ could have been dropped by many guys he fought, the problem was they could never connect or land flush. It wasnt until he lost a couple steps that people exposed his jaw. Im not saying for sure but I think the only guy who could put enough pressure and who was tough enough to take everything RJJ had to offer while he came in would be Hagler. He was a tough SOB, I think he is the only one who could possibly wear down Jones and possibly KO him. I dont see Hagler winning a decision, it would either be KO/TKO or nothing. Actually I think it would be hard to even corner Jones to hit him in the first place...his speed was unbelievable in his prime. An ATG for sure.