Give the server admin the option to set a default download quality just like streaming options.
Also, give the option to set a maximum quality for downloads just like streaming options.
This can help solve confusion for end users ex. my father went to download some films to watch on a plane, but the default download option on iOS and Android is to download the original file (which in my case are my BluRay rips at ~40GB each), thus surprising him when only one film downloaded.
On another note, please listen to mkv flags embedded in the file. some films and tv shows default to the wrong audio track even if specified and set in mkvtoolnix (Default, Original Language flags). Hidden Fortress, Seven Samurai, etc. play the English Commentary track and there is no option to override this setting to their correct Japanese track.