How about a graphic presentation in DVD Profiler for the subtitle languages or the ability to swap the text like with features and audio? The only problem would be that some languages are spoken in more than one country. So I think the flag for the country of which the language is originated from or appropiate with the CoO should be used. For instance the British Flag for the English language with Movies from Great Britain or the American Flag for the English language with Movies from the U.S.A.

This is just something that can be done in a layout surely? Doesn't require the program to be modified.