I think the market opportunity can be a standard and eventually get labels to include your standard in addition to their traditional labeling.

Figure out the variables (like shape, inseam, width, whatever else) for each article of clothing. Then freely distribute this and begin to catalog popular items. You can crowdsource some of this. The idea is people will look up the clothes as per your scale.

Then after you index a lot of clothes, you can search by exact measurements and then you can hit up clothing manufacturers to use their propriety code in their marketing or promote their brands on your site.