I’ve wrote an extension:
and submitted an issue to Hugo.
The implementation of the extension is as simple as it can get, but using the extension seems to enable generation of auto heading IDs on a par with Blackfriday.
I’ve pondered over and tried out some other options such as the processing in ox-hugo, but decided to stick to the basic after realizing how complicated the requirement can be from i18n/l10n point of view (see https://github.com/gosimple/slug).
cc: @kaushalmodi, @bep