She can't even perform her intended functions at the lowest settings. There's no point in keeping a unique character in such a useless state. I can make any random character do that just for the sake of it.
Besides, he could have played out an existential crisis, a re-evaluation of goals, and (partial) redemption. Kirishima isn't whispering in his ear anymore; he could look at the world differently. Wouldn't that be great?! I don't understand why you have to be so utilitarian with the characters.