Support lingering / persistent subtitles

I would like to be able to configure VLC to show subtitles for longer. This would be useful to me because I watch foreign language videos with foreign language subs, and I when I don't understand something I will pause the video so I can read the subs. But oftentimes the subs disappear before I have time to press pause.

Concretely, I'd like to be able to set a configuration value, call it subtitle_linger_secs, to a floating point number of seconds. Subtitles would remain on screen for subtitle_linger_secs longer than they normally would. If a new subtitle appears in that time period, the previous subtitle would get pushed upwards.