I'm a little late to the party, but I think this is the key question:
Shamefacedness is G127: αἰδώς. Only appears twice in scripture, the other being translated "reverence":
From lexicons, there is a hint of "downcast eyes" in the root words. Bashfulness, modesty, reverence.
I see this as key because it is the attitude that you see on a woman's face. It is the opposite of the attitude promoted by feminism. Most women in the world today have harsh faces, but a Godly woman has a soft demeanour that just shines out of her eyes. She is not self-promoting, but is naturally submissive and reverent - first to God, secondly to her father or husband.
This I see as the key to the entire passage. It's not fundamentally about clothing - clothing is a symptom. It is about a fundamental attitude that women are to have. An attitude that is not arrogant, but loving and respectful. When a woman has this attitude, she has shamefacedness / reverence and sobriety / self-control.
And then this fundamental attitude causes her to make sensible decisions in the clothing and hair departments. These decisions are compatible with the foundational attitude, and do not contradict it. But there are not firm rules on skirt length or whatever, because it's not about clothing per-se. A woman can be dressed top-to-toe, but if her face is arrogant the clothing is meaningless. While a topless woman in an African village, who is however unwilling to make eye contact with a man due to traditional modesty, is acting far more modestly than the first woman. That is not to discount clothing, as the woman with that attitude will choose to wear whatever in her culture will emphasise or at least be compatibile with modesty. But clothing is the symptom, not the fundamental issue.
And the more a woman's face shows this attitude, the more beautiful she looks.