Cool systems, a touch of feedback
I think the class/job system is actually really well conceived overall, but now that we have both I think a couple of changes would make a lot of sense, even if they would require rebalancing:
1. Remove restrictions on cross class skills for classes.
2. Let jobs equip more than one weapon type.
Now that end game is mostly ruled by jobs, I don't see the point of having restrictions on cross class skills at all. I want to equip Fire on my Gladiator - so what if it's weak? Any skills you would need to perform your role adequately are already bundled into your main class. This would just open up fun options for personal tailoring.
Class themes are based around weapons, but job themes are more about aesthetics. I just think there should be more cosmetic options for a given job. Many warriors in FF traditionally use Sword & board, so it should be an option in this game. It would also improve the scalability of the job system and help them stand out more.