benignuman –
Covering the hair is a completely different sugya; it’s not about tznius. It’s a gezeiras hakasuv, so whatever its rationale it isn’t really relevant to this discussion.
It is obvious that the Beis Shmuel is a dochek, since pashut pshat is the Rema’s whole point is to say even ???? ????.
http://hebrewbooks.org/pdfpager.aspx?req=9727&st=&pgnum=149
At the end of the day, you’ve found me a makor – which I do not agree with l’halacha – but a makor nonetheless, that one may not gaze at ???? ????. But the bottom line is you haven’t sufficiently demonstrated that the legs or any other body part are of that status. Admittedly it is your reading in the Gemara (Berachos 24a), but a) I am not convinced of the svara of that reading (#1 because why should it be that way and #2 because it is quite a massive dochek to say that the Gemara intends to differentiate between legs and hair/voice without telling us), and b) that reading is contradicted by the fact that ???? ???? is assur l’shitascha for everyone, while legs are explicitly only ervah for people who are arayos.
When we began this discussion I was asking for a makor, not a rationalization. I understand that those who believe women are always obligated to cover specific parts have pshatim in the Gemara and poskim which fit their view, but I have yet to see a true makor – i.e. a Gemara which according to the simplest, least dochek pshat, or the pshat that is explicitly the consensus of the rishonim, that mentions this obligation.