Hiinokami
Darling in the FranXX, alternative universe: Journey of Return
What if Zero Two's Body was brought together with the Squad 13 since they come to space, for rescue her mind, re-connect both of them. After this, destroying Virm's homeworld and the story that all we know, but different in just one fact.
At this point, when they reach and can activate the Klaxossaur Bomb, they not necessarily dies. Rather that, in some form, the cockpit could have some of hibernation chambers (due the fact that they "veeeeery" distant from the Earth planet) for the survive in their way trip back to Earth, that little moment could be between the activation of bomb and its explosion, just like the ejection system for stamen and pistile, but this time, ejecting the normal Strelitzia.
In the meanwhile the Squad 13 and the rest of humans could be recreating the civilizations and growing up, but after some years, Hiro and Zero Two would arrive on Earth, but very distant from the society, however still on am ambient with very much life and nature, like rivers, trees, and et cetera. Trying to survive, they would fight to return back to their friends.
PS: This is story is just a way for me train both my english and reasoning of construte a text, it will have some failures and errors, even if I try to fix them as much as possible. So, i open to suggestion and critics, I hope at least not wasting anyone's time.