Not to replay though. I can't see new rank storyline content is unavailable to you because everything's 50'ed. We get WHM, BLM etc now but I really, really think we'll get new jobs at 2.0 as well, at least to sucker PS3 owners into picking it up. The answer is unlock a new job, level it, get to the rank requirement, and do it.

(though judging by the rank storyline missions in current game, you can do the 10, 15, 20 ones at any rank above that, so I can't really see, with respect, what you're getting at...)