rabbiofberlin,
I think that concert made your thinking go a bit wobbly! (joke)
Beged Hiddur – So pants, surely an important particle of clothing, would constitute hiddur. Yet surely you are moida that regular usage of pants by a female (c’v) is not covered by the beged hiddur exemption, as there is no special cause for its usage (like cold or rain.) So the Bach’s situation is inapplicable in this situation.
Now, even if you taaine it is NOT hiddur, you seem to be whitewashing the tznius problem. A miniskirt (c’v) is not a Beged Ish either. Yet surely you are moida that it is assur due to tznius. So how can you allow pants, EVEN IF lo sibash IS inapplicable!?