PM: There are other Heterim used that are more Meikil than R’ Moshe’s. To answer your question, if hypothetically a woman got a legitimate Heter to wear a miniskirt in public, then, while I would not personally look at her, I would have no right whatsoever to try and force her to wear longer skirts.
Even better: what if the boss finds himself attracted to a woman? She is perfectly Tznius and follows Halacha to the letter (or past). Is it her fault? Should he fire her or realize that since this problem stems from him he has to find a way to fix it without affecting her?