Bespoke clothing websites for dress shirts and suits are a dime a dozen. Can the same model be applied to daily, basic wear such as shirts, sweaters, etc.? I can appreciate scaling may be an issue, but I think there are appreciable margins and a real niche to fill.
I've worked in the fashion industry for several years with and with numerous manufacturers. I think it is because it costs $$$ to make bespoke products. Generally consumers only want to pay $ or $$ for basic clothing. You would have to figure out how to sell basics for $$$. Let me know if you'd like a follow up!