So I like the Idea of the commander sacrificing their levels in order to give them to their comrades. But it would be cool if the commander could somehow regain levels. Maybe when the comrade defeats the enemy the experience goes to the commander and a maiden is somehow able to distribute that experience through a faith oriented ability would be a good way you could describe it in lore. You could even go further with their being consequences for relying too much on this maidens abilities is the development of certain fetishes even after the regression is reversed. This could provide some really fun gameplay and story elements. Such as an option that unlocks once a fetish reaches a certain point where you or one of your party members can willingly regress a stage while still having the option to go back and look at past content without having to start over.