No one wants liability. Builders wants to build and be gone ASAP. They'll build a $350k home using the cheapest parts and labor they can find and do their best

No one wants liability. Builders wants to build and be gone ASAP. They'll build a $350k home using the cheapest parts and labor they can find and do their best to run away with the profit. 5 years time, after any sort of warranty, their workmanship (or rather, their lack of it) starts showing. I think your idea would be great, but there would be turmoil while the liability hot potato is thrown around until the industry figures out where that lands (probably some form of "malpractice insurance" on builders would become a thing, with higher premiums on those who suck more, eventually forcing them to be better or quit entirely).