yeshiva guy, may I point out that the question of ervah will not apply to women. Additonally, I lived in a different country where sunset was very late and it was common for MEN to daven in the train as they could not do it before then.
And why do you want to deny women the right to daven? Actually, they are “MECHYOV” in tefillah as tefillah is NOT a mitzvah shehazman geromo. It is just the faxct of the organized, three tefillas that they are not obligated to do, but tefillah itself is part of their chiyuv.