Just as proposed on chrippa/livestreamer#1187 , I believe this will incentive contributions to the project.

After submitting my analysis on a streaming site to help create a plugin (chrippa/livestreamer#1156) that didn't get any traction, I was looking at the code and searching around for documentation on how to develop a plugin myself, but with no luck other than a short answer at the forums (https://groups.google.com/d/msg/livestreamer/TmVKnud0KRc/hDvURFUjrM0J) and it felt a little overwhelming to reverse engineer the plugin and related code code.

I believe that with a little help / article on plugin development, it will be possible for many contributors to add additional community plugins (albeit simple ones). Other option may be take a plugin and post it as a sample with full code comments (ie which functions are mandatory to be developed for a new site to be supported, what those functions should return to core code, etc)
Thx, Wolf