Have you considered setting up a selection datatype for country? See http://ez.no/doc/ez_publish/technical_manual/3_9/reference/datatypes/selection and http://ez.no/community/forum/general/how_would_you_make_this_in_ez_publish. It may work as long as you never delete a country.
Using an object relation datatype in the course, internship, and other classes that is related to a folder's content (could be country or anything else).
Or, leveraging the tagging functionality in 3.9.2 The good thing about the tagging functionality in this last version is that it does not require related nodes to be of the same class.
All in all, this is definately not something hard to do.
Good luck!
Felipe (Just got the Certified Extension Developer title!!!!)
Felipe Jaramillo
eZ Certified Extension Developer http://www.aplyca.com | Bogotá, Colombia
