PBA: The interesting part of the end of that is that the Mechaber (and Rambam) says the Oved Kochavim wants to be Ma’avir Al Das. Presumably this is because they couldn’t fathom/it would be incredibly abnormal for a Jew to force this, though the potential Diyuk is interesting (but wrong, I think). I would think that Ad’raba, Sha’as Hashmad might apply since this is a law forcing you to be Over. What makes this so complex is that they (I think) had Poskim Mattir it for them, so it’s hard to call it Yeihareg V’al Ya’avor for some but Muttar for others. Especially because if there is a Heter, then the army is no longer intending to be Ma’avir Al Das.
The Ervah part is interesting. As far as I know, no one says that seeing a non-Tznius woman is Yeihareg V’al Ya’avor. It’s not a Davar Hamevi Lidei Ervah. Especially by Kol and S’ar, since those seem to be lower than the rest in many Rishonim.