I believe Tesla’s FSD is already better than such unassisted drivers. Particularly with the current FSD limitations which require monitoring driver attentiveness. If every drunk who attempted to drive was using FSD, deaths due to drunk driving would be virtually eliminated. Heck, even advanced lane keeping and smart cruise control from other manufacturers, while much more crude, would still help tremendously.
I wonder how much of drunk driving crashes are because driver turns into speeding asshole vs dozing off. You wouldn't be able to force them to use FSD, especially in a fun car like Tesla. Maybe if it derated itself if it detects erratic driving. They already released a feature where it avoids crashes even when FSD is disabled (but does require subscription).