Im surprised I love that Neptune and Mars arrow scene as a nightmare drabble but hate it in canonical context
tldr mars being a character who does questionable/mean things for the greater good is already established as being her thing and a reason to tolerate her being kind of a dick sometimes, why does this need to be proven to someone we saw who couldn't make sacrifices either (which was in fact framed as a good thing) and framed as a ~life lesson~. Basically why use the most inappropriate senshi for that scene, its not like makoto got paired up
But in the Nightmare I think it plays on a fear of Michiru and the Outers in general have. Whatever flavor of canon, they always try to make peace about working for the greater good, but one interesting snag is they always manage to keep agency about it. Whether to choose to be ‘mean’ or choose to throw themselves at an enemy and be a meatshield, its a choice. I think the idea they’d be ordered/cajoled into cannon fodder and have no real choice in the matter and maybe not even know they’re expected to do it until it drops on them scares the shit out of them