I used to have a method to do this as I love creating fictional nations. I have a fictional file from older versions where I made Anguilla a Faroese dependency so everyone born there would play for Faroe Islands instead of Anguilla or the UK. Apparently I also did the region trick, but moved the Faroese regions from the Faroes to Anguilla so the players are born in FI but are of Anguillan ancestry.
For some countries (like when I try to create a Russian-language country in Africa) like Lesotho, the game needs me to move the cities to another country and the clubs too or else it continually generates local names and not the region/languages I've moved them to.