Dumping some nip34 thoughts:

 1) maintainer opt-in feature
 2) allow list or WoT based
 3) must be clearly communicated to potential contributors in clients
 4) could specify rules that could be implemented in a ci environment via a DVM. Eg. Must add or update tests, or must pass standard ci pipelines. A DVM could run the checker against the PR/patch set and respond with a specific comment before the PR gets shown publicly and to the maintainers.