I've investigated this a bit. It seems that because we let vid.ly do the setup we can't register plugins. There may or may not be other ways but I'm hoping for a response from the JW Player email support.
Uh. I was wrong. There are other simpler ways to make it work without messing the way limited API JW Player exposes. It's just HTML5 after all. It's just div tags and stuff sitting on top of a <video> tag. With a little bit of jQuery I've got a brilliant prototype working. I don't have the database backend to save or even make these snippets so they're hardcoded but it's working really well. I'm eager to demo the prototype and then we can discuss what to do from here. It quickly becomes a matter of CSS excellence. :)