Not to be too simple minded, but:
Couldn't you render the video as if there were no subtitles requested.
Then create a brand new text window for the subtitles.
It is quite a handy feature if you are trying to learn Korean (or any non latin script). You can play the movie, watch the subtitles, and listen to the pronunciation. There are many features that would help one to learn a foreign language by watching DVDs, but A/B replay is certainly one of them.