This is a single thing i realize in beach arc:
"(Cooking ver.) Mina is good and charming BECAUSE she is a robot, act like a robot and look like a robot. An incomplete human emotion with all its flaw in expression and understanding."
Just look at super Mina (the human like outer with extra power), she is human-like robot. If MC marry her, is the story will be as good as this? I dont think so... It will just like MC has romance feeling for a child-like adult (considering Super Mina is like a child that cant use her full spect at optimal use). She doesn't look like a robot and doesn't act like one. Just like a kid in (super) adult body.
You can get attracted by all the good side in person, but when you stay and rather comfortable by all the flaw in them, it's when you know that you love them.
Thats how i know i LOVE this story.