Michael Watson was a very skilled smooth boxer who was able to beat Nigel Benn and should have took the decision against Eubank although for some reason the judges didnt seem to think so. Watson was also doing very well against Eubank in the rematch before the tragic consequences of that night in round 12. He was also adept at counter punching and I feel he had the ability to keep Calzaghe at bay by outboxing him to win on points.
Mike was a great all-rounder, but i think he really was suited to using those skills against Aggresive and/or Wild Punchers, Guys like the then hyper Nigel Benn, and dangerous Don Lee who had humbled Sibson some time before, Mike was not a destructive one shot hitter, but he could place them well and would discourage, a sort of UK version of James Heat Kitchen, However, Joe has a great Chin, and can Box, and has very fast hands and good movement, so i dont think Mike will find Joe very easy to block and counter against, also if needs be Joe can stay at range and Box for awhile if he does start to get countered, so Joe's verity might be what swing it his way, Never easy against "Watto" but i think with Joe's great Stamina he can stay ahead of Mike for the Points, perhaps Close but clear.
Watson was great but his style is good for Joe. I think Joe would just keep touching him. I think it would be an absolute war for 12 rounds but with Joe winning late or 7-5, maybe 8-4.