Would it be possible to have a final skill maybe at level 100 where you become your own summon based on your class and unleash an all out attack, defense or heal on the NPC or party members. Kind of like Terra from Final Fantasy 6 was able to transform. While transformed a new skill bar with maybe 3 powerful skill would appear for you to use. Unleashing a fun amount of gameplay on bosses or adds. Maybe let the new skill be like a personal limit break for each class.

For example a PLD would embody maybe King Thordan. WAR would transform to Titan and each other class would have their own.

I know the visuals are a lot of work but perhaps it doesn’t have to be a full skin of that summon. Perhaps a aura at first around the character. Maybe as time goes on the visuals could evolve like a relic weapon.