Is it possible to 'Mux' subtitles of more than one language into a single subtitle (.srt, .sub) file, and have DVS display the option of selecting the preferred language during playback?
You can have multiple srt streams of different languages, but you can't have a single srt with multiple subtitles, since it doesn't support overlapping time codes and if it did, you couldn't select. Same goes for .sub if you mean the microDVD text format. VOBSub (.sub/.idx) can contain multiple streams.
For PC playback you would be better off with multiple textsub streams and for SAP's you would be better off using xsubs. Anyway: http://forum.doom9.org/showthread.php?t=78718 Not sure how you would go with multiple streams though since I never tried it.