I love this. The balance between your internal confidence and your presentation in the face of others is a central point of modesty. You summarized it very well.
I think an expansion of "modesty" as it is usually discussed is the way to go. Add to the discussions of dress the mindset of how you choose the outfit. Then expand from there. Why do you choose to wear jeans and a t-shirt? Why do you choose to wear a skirt or a button down shirt and tie? Asking the why helps get to what should be the driving motivation. And the driving motivation should come from a modest approach to life.
Regarding the unfair balance between men and women, I think For the Strength of Youth is a good example. Most of the "Dress and Appearance" article is targeted to both genders. I have quoted the main paragraph that addresses them separately below. (After this, each does have a specific address - women to wear only one pair of earrings, men to "dress with dignity" while passing the sacrament.)
The young women are given very explicit directions of what constitutes "immodest clothing." Young mend are told to "maintain modesty." When I was young, young men liked to wear pants that were falling off so that their boxers showed. They dressed slovenly and sloppily in general, but the loss of pants was a frequent risk they ran. But does the book tell them to wear pants? Nope.Immodest clothing is any clothing that is tight, sheer, or revealing in any other manner. Young women should avoid short shorts and short skirts, shirts that do not cover the stomach, and clothing that does not cover the shoulders or is low-cut in the front or the back. Young men should also maintain modesty in their appearance. Young men and young women should be neat and clean and avoid being extreme or inappropriately casual in clothing, hairstyle, and behavior. They should choose appropriately modest apparel when participating in sports. The fashions of the world will change, but the Lord’s standards will not change.
https://www.lds.org/youth/for-the-stren ... e?lang=eng
I was discussing this with my sister, and I decided that I will never be called to talk to the youth about modesty. Which is good, because I would spend 30 minutes detailing how young men should dress. And end by telling the young women "make sure you dress presentably as well."
I wish I would get called to give that talk.