There's plenty of things adjacent to skimpy armor in such games that Susan could take issue with, don't you worry. She's just not going to complain about the armor itself unless it clashes with the tone or something.
In terms of actual armor, I originally just imagined Nanase wearing armored gloves that didn't go past her elbows. From a purely aesthetic standpoint, that would be my preference (I'm allowed to like the aesthetics of swimwear inexplicably combined with boots and gloves, okay?!).
In searching for references for armor, however, I wound up watching some of a video on how medieval armor is put on (ye GODS is it a process). From that, it is my understanding that shoulder plates like these were connected to the torso armor, and wouldn't work with a bare torso.
So, of course, I immediately decided she had to have shoulder plates in order to maximize the absurdity.