If you are lucky – or not lucky – enough, your customers might be mainly goverment organizations. As such there are no choices to be made, disputed territories or disputed names. You would simply have to follow the conventions and rules of the specific government. What is recognized by the country, it is your target as a developer. And there are online documents to be followed.
For example, here in Germany the Auswärtiges Amt (German Foreign Office) provides the Verzeichnis der Staatennamen für den amtlichen Gebrauch in der Bundesrepublik Deutschland, the directory of state names for official use in the Federal Republic of Germany.
A separate document is available as well with information in multiple languages: German, English, French and Spanish.