Suggestions below for innates just to get the brain juices flowing, but I have no idea what is feasible or not, no modding experience.
1: Faster charging limit? IE if sad then limit charges as normal, if normal, it charges like you had fury
2: Charging limit gauge based on another character using a limit
3: Charging limit based on party members taking damage also
4: Mechanic to alternate between physical and magical attacks, such as after a physical attack, next spell cast consumes 50% less mana, and after a spellcast, next physical has luck increased by 50%
5: Critical hits always leech (hp or mp)
6: Automatic character postioning in correct row, IE if casting a magic spell, automatically move to back row. If attacking with physical, character is automatically moved to front row