I've thought about it and I actually have... three characters had in mind should I ever take that route. That would be:
D or Nancy:
I feel D is a no-brainer. A chunibyo as a main protagonist in a stick figure universe where anime characters resurrect is like the perfect setup. I feel like I would've totally started off the series with him if things played out differently. Would love to explore a spin-off series with him though.
Nancy on the other hand, I feel like she would be a wildcard pick. She obviously knows more about the world and everything going on. It'd be great to see her be this cynic and slowly grow to be more optimistic.
But I feel like Nikado would be my first choice:
I remember watching Fist of the North Star and they killed this character and they were like "Oh hey, meet this similar character c:". It'd be funny if I explored that trope (THEY DID IT IN DEATH NOTE, although I'd argue they did it more creative there). Especially him finding himself and becoming more of an individual.
What about you guys?