Review approaches to local storage of pub data

[metasj]

GDPR inspired a discussion about how to store user and other data about a PubPub community inside a {country, region} that does not want any identifiable data shared outside its borders.

One resulting idea was a 'Heidelberg node', which a community such as CURSOR_ could use.
The specification for such a node needs review and iteration, from Thomas and Travis. Is that description helpful, sufficient?