I like the concept of a class->Job system.
I think it would also be great if they could expand on it in a way similar to what you see in the FFT games.
The jobs we have now would represent basic, tier 1 jobs. In later expansion content they could add tier 2 jobs, which require some combination of a job and 2 classes, or two jobs and a class. These tier 2 jobs wouldn't necessarily be more powerful than tier 1 jobs, but they could be more specialized. A ninja could be a combination of a theif ( if they add it) a warrior, and a gladiator. This job would lose the defensive capabilities of the warrior job, and focus on pure melee damage output, with low hp but high physical evasion. (susceptible to magic damage). effectively being a melee version of a BLM, with high damage but low survivability.