> As a naive guy

I intend this reply to supplement your list of challenges, all of which are valid. I hope this helps convey an additional depth of complications in designing women's elastic support wear that may not be immediately apparent.

> You've got a data capture problem

The missing piece here is the intersection of: clothing "fit" problem, where each person's body will interact with clothing at different points; the gravity "g-forces" problem, where the clothing is required to bear weight at every step without tearing apart; and the appearance "fashion" problem, where different shapes carry that weight at different points.

I'll take apart t-shirts first, and then switch back to bras.

Given several men of slightly different torso composition, a simple men's t-shirt can interact with their belly, lower waist (shirt length), ribcage, nipples (ask any runner), armpit, upper arms, neck. At each of those interaction points, the clothing must fit 'correctly' as perceived by the human being. Each human being has a preference for each of the listed areas, and will complain about poorly-fitting t-shirts if they do not fit 'correctly'.

I require loose armpit and long length shirts, among those seven options, and have more or less given up on ever finding a solution for my abnormally-shaped ribcage. So I typically end up in men's XL, because it provides enough 'airspace' to smooth out my torso and extends low enough to keep me from flashing people.

Someone else with the same torso length, torso diameter, and waist measurements might choose a Medium instead, because they have a decked-out bod and want to show off every curve. They'll need shirts made with more stretch than mine, or else they'll rip the armpits open waving hello to a friend. Shirts designed for a tight fit use a different 'cylinder' cut than shirts designed for a loose fit, so you can't just put them in my sized-down XL because I've been selecting for a different cut of shirt than is appropriate for their desires — and you can't just shrink all dimensions on an XL by 30% to get a M because human body parts don't shrink at the same percentage rate.

So, you can evaluate the 'fit' of t-shirts based on these criteria, none of which can readily be captured by 'shape data' alone:

* Does the shirt show off, or mute/hide, your physique to the degree you desire?

* Does the shirt rub uncomfortably, or rip/tear, when you move while wearing it?

* Does the shirt fabric irritate your skin, at your desired tightness?

You can custom-bespoke every shirt to a person's shape, but you'll still have to make fashion decisions ('drape', for example) that will include some and exclude others. If you end up deciding to print custom-fit "perfect mirror of your shape" fashion, that is fashion, too, and I would loathe it with all my heart because that is not what I want my clothing to express.

Moving on from the t-shirt analogy to bras, there are additional problems that bras have to solve for, that t-shirts do not:

* Bras are held with elastic against an extremely sensitive area of skin for hours at a time (sweat is a primary concern)

* Bras need to provide front and back appearances that matches the desires of the wearer (padded, unlined; demi, full coverage, balconette, push-up; longline, racerback, strapless)

* Bras need to provide support for 'weight' anchored to both sides of the chest (US average ~3lbs/side, K cup ~8lbs/side), that can cause pain every time you take a step, encounter small vertical G-forces (stairs, elevators, cars), or large all-directional G-forces (cars, subways, sports)

* Bra elastic loses stretch over time, due to wear and tear from the thousands of G-force events per day they intercept and reduce bodily impact of (adjustable straps, multiple rows of hooks, discard and replace occasionally)

So, not only do you need shape data, you also need "fashion" data, "fit" data, "fabric" data, and "gravity" data. You need data about composition — density for compressibility, shape for support and fashion, total weight for structural integrity — that you can't measure at home easily if even at all. You need material that can stand up to being punched from within a million times that also feels comfortable when held skin-tight all day. You need to make it fashionable, while keeping it fashionable across multiple size vectors (band size can vary from 24" to 48" or more, cup size can vary from 1/AA to 8/H or more). You need to transfer G-forces from the wearer's chest to the elastic while not digging into their skin more than they can bear (bralettes, underwires). You need to plan for elastic weakening over time (adjustable straps, multiple sets of back hooks).

Many men only see that level of tailoring in bespoke suits/tuxedos, and wear them once a year or less, and suffer no consequences the rest of the year. Many women have to wear one every single day, or else they suffer chest pain (F=m*a with only skin and ligaments to bear it) and/or societal outrage. It's a really intense market to try and serve.

I hope this helps.