[masteryod]

Hi. I was thinking about this for a long time.

Many movies have multiple audio track and can have multiple built-in subtitles (or as separate .srt/.txt files). It would be so nice to be able to select preferred audio stream and/or subtitle language on hitting "play" button.

I guess it would work like this:
==Default XBMC Language Setting==
"Preferred audio stream: <default>"
"Preferred subtitles: <disabled>"
"Ask before playing: <no>"

I would change it to:
"Preferred audio stream: <default>"
"Preferred subtitles: <eng>"
"Ask before playing: <yes>"

Then on hitting play in library mode, if multimedia file contain multiple audio/subtitle track (or when there's more than one .srt/.txt file in directory), instead of playing a movie an additional menu would popup:

Audio and subtitle set-up for this movie:
"Audio track: <eng>" - this should list also commentary etc. just like good old dvd setup
"Subtitles track: <disabled>"
"Subtitle file: <eng>"
"Remember my choice: <yes>"

But this time you'd need to pick only available language.

I guess .srt/.txt files would have to be come with additional markup tags or name tags e.g. [ENG].The.Subtitle.2014.srt

What you think about it?

[da-anda]

should be doable by an addon. There already is one for extended subtitle and audio stream selection rules - it could as well show a dialog (if it doesn't already). Don't remember it's name though, so you have to search for yourself or maybe somebody else can help you out.