If Hina died that would completely invalidate 2/3 of the manga. Draken too. Mikey dying would also fall more into "some people can't be saved" than accepting loss and moving forward, which seems at odds with the series. I think most of the Touman captains, Hina, Naoto, and Akkun are safe because they're practically a requirement for Takemichi to stop time traveling. Anyone else is fair game.
If the author goes for the shock ending, maybe Takemichi rather than Mikey, but thematically it would be a questionable choice as it would just be a repeat of Shinichiro's death for Mikey.