I read Inspired Inventor Tensura and loved it. I want something like that but more battle heavy and I'm doing it in Naruto.
Why Naruto?
Because we have the Otsutsuki. although their inclusion in the original story was out of nowhere I believe they have infinite narrative potential. Most fanfics of Naruto end when the MC either takes over the entire Naruto world with Six Paths power levels and kills the couple Otsutsuki clan members that invade.
I want to create an MC who will spread across the stars and fight the Otsutsuki clan as a whole across the stars. An immune response of the universe to the space parasites.
My idea is to have the story be sectioned by the technological advancement over long time spans like a cultivation novel. The first era would be just him advancing civilization and using biotech to become biologically immortal.
Next era is a cyberpunk era. With some minor space ventures and a full confrontation with Kaguya and Isshiki.
I'm going to have that confrontation destroy that civilization paving the way for Naruto Canon to exist but with advanced technological remnants. However the tech on other planets remain and the MC keeps on advancing.
After this MC will start approaching true FTL and the true war for life against the Otsutsuki will begin.