Marble is using the CIA World Factbook for displaying country information. Have a look at the python script marble/data/ciasource/cia2kml.py and use it to compile the latest information from the latest version of the Factbook: https://www.cia.gov/library/publications/the-world-factbook/ Once done you need to do some extensive testing to see whether the information got properly applied.
https://github.com/twigkit/worldfactbook-dataset might be a good base as well.
I was just wondering if this bug has already been solved by now, or is it still valid? :)
Please follow up in https://phabricator.kde.org/T4262