The only person I could see doing that here that I know of would be Captain Maxx, because he does that all the time.

I have only had one character master one job. It was on III DS, and I had Ingus as a master dragoon.

I simply don't have the time or the patience to give everyone mastery in all jobs, let along them just reach level 99 in any game. The only character I've ever had reach max level was Squall at level 100 in VIII, but levels aren't hard to come by in that game. There isn't really any reward other than being able to say "I did it," so I don't see a point.