After I attained level 50 and completed the story, got my mech mount, starting labyrinth, got my relic...etc (you get the point). I got bored playing my character on another class.

My idea is this.

Once you have 100% completed the story quests, allow your character to reset just story quests.This way when you change your character's class to one you've never played before, you have motivation, incentive to play that class to 50.

To make sure that people don't try to abuse this in any way as a way of power leveling, make it to where once you reset the main story quests, they HAVE to completed 100% again in order to reset it for yet another class.

I hate that my character is now destined to fate/dungeon run for the rest of its days.
With this option, I would actually spend my time more on my one character instead of having to create a new one with the class I want to play next.