from http://country.io/continent.json you can have both countries to contenents and give Countries valid cities eg http://country.io/capital.json Which means if you can defined a key-value pair you can create more accurtate test data that placing "St Petersburg" in "Iceland" which is the current option.
At worse if the json file was downloaded and 'mounted' as a table would be useful. But really JSON is the new datasource that Red-gate has to connect to.