Wigging Out

Hirhurim (my 2nd favorite Torah blog), takes up the issue of sheitels.  This is a question that many of you often raise, so many of you have already heard my view on it, but for the rest of you, hear it is (and frankly I'm surprised that something like it hasn't shown up in the comments there - maybe I'm wrong; it's a very learned crowd):

Rav Moshe Feinstein (Igrot Moshe, EH 2:14) famously addressed the issue of men and women riding the subway in close quarters.  His response was that it is permitted to ride because most people don't find that to be a context that leads to hirhurei aveira (improper thoughts).  However, if you know for yourself that you are an exception, and it will result in hirhurei aveira, then it is prohibited for you.

This teaches us that there are certain rules in the realm of tzniut and arayot that are subjective (they are prohibited because they lead to hirhurei aveira), and others that are prohibited simply because objectively, they are articulated by Chazal as erva.  Most laws of tzniut will fall into both categories, and therefore we are required to honor both the letter and spirit of the law - see Rabbi Student's example of the anatomically correct body suit, or clothing that covers everything but is too tight.  While it may fulfill the letter of the law by covering everything that needs to be covered, it fails the halachik test because it actually causes the type of reaction that the entire tzniut system is looking to avoid.

Hair is not subjectively erva - it doesn't usually lead to hirhurei aveira; the biggest proof is that non-married women don't cover it.  It is difficult to believe that the exact same hair that a week ago was innocuous magically becomes alluring.  Therefore, married women need to cover their hair because they do - because it's in the list that Chazal drew up about what needs to be covered.  If so then it is the letter of the law and not it's spirit (there is no spirit) that needs to be followed, so a sheitel - even of her own cut hair, even if it looks better than her own hair - fulfills that requirement.

I wonder if similar reasoning can be (has been?) used to defend those who are lenient about kol isha when it is not heard live.

What do you think?