In response to (most of) the continued commentary here.
This issue is not the place to make pitches for use-cases.
While we (Mozilla) are definitely sympathetic to use-cases that help users, a better place to capture those is either on your own blog with blog posts, or perhaps as pull-requests to add them to the respective Explainer, e.g. in this case:
https://github.com/WICG/serial/blob/gh-pages/EXPLAINER.md
Better yet both, so you can fully express the use-cases yourself and then cite them with a brief summary in the Explainer.
On the specific medical use-cases provided, if anything these are great examples both in terms of greater potential harm to users, and more vulnerable infrastructure due to systemic IT process issues. Those are both good reasons to expose fewer potentially risky features, not more.