Charliehall, Rabbi Broyde is a Modern Orthodox Rabbi. I do not accept his count-down of the shitos without seeing at how he arrived at his conclusions inside. Again, the Gemora in Kesubos 72 is clear that the ikar hair-covering is min’Ha’Torah. Shitos claiming otherwise would be hard-pressed to explain the Gemora. The opinion that it is a minhag sounds extremely shvere, if it even exists, and is not the result of somebody’s extremely shvere interpritations. And if you start going for far-off shitos, I know of a teshuva from a Hungarian (pashtus, Chassidishe) Ruv who held that a lady who does not cover her hair is misosa b’yad kol adam.
And if it were de’rabbonon(eventhough, who told you that we go with those shvere shitos), so what?? De’Rabbonon does not mean “mutar”.
And again, what are these MO ma’asos? Going after minority opinions or da’as yehids., including very shvere ones. Or dreing up even those minority opinions or da’as yehids(like it happens in some cases)?