its kind of like Jeht from FFX, it would make a great twist. He becomes a Zetsu faster than normal from the infinite tsukyomi because he willed himself to do so and retain his consciousness and then eats the newly born shinjuu fruit to gain power to save Naruto from Kaguya's overwhelming power. Yes Kaguya is so strong they cannot defeat her, then Zetsu Iruka comes and has shinju powers and defeats and absorbs Kaguya. But Iruka begins to lose his mind to the fruit and it gets really emotional because Naruto must seal his original father figure.