It's just a quick idea I had. Since right now levelling other jobs doesn't grant you any advantage...I mean it doesn't matter you got the title God of magic, if you are ninja it doesn't affect you at all

The idea would be introducing new skills based on jobs where you reached max level. For example if you have a lv70 black mage, you unblock a special type of Foul. This Foul could be used on other jobs. But if for example you are a healer using it, the damage would be calculated using the mind stat instead intelligence.

Since this could be too op to be used without control, these skills could substitute limit breaks. There isn't a great difference between the Foul I'm talking about or a caster limit break. The difference is now everyone who levelled a black mage would be able to use that limit break. In case they were limit breaks the calculus of damage would be different and no like I said before.