I'm not sure if it is a niche large enough to be a viable business, however. In some areas, I source as much as I can from local providers - or use my own labor. However, that's probably not realistic for most folks. I'm fortunate enough to have an obscene number of acres and live next to a small family farm.
Of course there's quite a lot of bad behaviour happening among such a dynamic development, but I wouldn't actually worry too much about anything that goes into a car. It's almost all high tech, and really not amendable to be manufactured in sweat shops. Plus car manufacturers are large and brand-conscious, and tend to tightly control their supply chain.
Textiles are at a much higher risk of being manufactured under bad conditions, but even there I believe the race to the bottom is coming to a natural end. Over the last decade, they have moved first to China, then on to Vietnam and now, I believe, indonesia and Cambodia. They're quickly running out of countries with lax labor standards.
Umm...
You know what might help? Blockchains. This might actually be something that could help with. It'd be an immutable ledger of sources. It'd not be perfect, probably. But, it might help.
Additionally, I'd pay more for something like a Fair Trade automobile. My daily driver is a BMW. I'm pretty sure half the computer components were made by Asian children and/or an abused populous. It's one of the higher end models, nearly six figures, but I'd have happily paid something like 20% more - if it ensured the parts were sourced ethically.
German auto workers are mostly paid quite well according to collective agreements, similar to low-mid level knowledge workers. And for cars made in Europe, not that many parts are sourced from outside of Europe.