I think that the topic of biblical modesty for women is one that is both of prime importance and practical significance. To that end, I would like to submit a view to be considered, namely that a legalistic dress code is equally sinful when compared to immodest dress.
"Being more conservative than scripture is no more praiseworthy than being more liberal than scripture." - Doug Eaton
The problem of the legalistic dress code is that it does not allow two important things. First, it denies woman's ability to live the gospel out in their dress, and instead it forces women back under the law. Second, it defines what is 'modest' generally in terms of Historical American dress, and thus, defines the bible's concept by our culture. Let me give an example. The blog Modesty tells us that " Modest dress is dressing in dresses or skirts [...]" it continues to say that if a women isn't covered from neck to ankle, with full sleeves that "she is dressing like a harlot." I would love to hear this women try to give a biblical guideline, for someone of a non-american culture. I also loved the womans statement after showing some photo's that when asked about these womens dress she states, "If he is a real godly man he will tell you that these women look like harlots." The arrogance that is present is staggering.
Looking at the Bible:
The bible speaks of modesty at several points, most clearly, 1 Tim 2:8-10. It is also noteworthy, that women in Proverbs 31 is never said or give a specific mode of dress other then she is clothed with fine linen and purple (ESV).
I desire then that in every place the men should pray, lifting holy hands without anger or quarreling; likewise also that women should adorn themselves in respectable apparel, with modesty and self-control, not with braided hair and gold or pearls or costly attire, but with what is proper for women who profess godliness--with good works. (1 Timothy 2:8-10 ESV).
The questions to be answered are, what is respectable apparel, and what is costly attire? I don't think that these questions have a specific answer, and by that I mean that the answer is different for different cultures. In some cultures, that may mean neck to ankle, in others it may mean something less. I can only imagine that standard being applied to places where weather would make that impossible, or where it is still only hide that is used for coverings. My point is this, we must allow the gospel to define modesty for us, not a set of rules. We need to function from grace and in a manner that is set at glorifying God, not obeying the law.