Wow, the "History" section of this really brought back some memories for me - three or four years ago, I spent a while working for a company who had a generalised video solution based on Adobe's OSMF, to which we also added many features, including a quite complete implementation of TTML (W3C's XML subtitling standard, which I'm not sure anyone actually uses).
It seemed to us at the time that betting on an emerging framework and (what we thought would become) an emerging standard would result in something quite useful. What we ended up with was a very complex and fairly miserable project which was eventually replaced with something much, much simpler.
In the early 2000s, it was possible to have an XML-based (SMIL) playlist which could seamlessly stream video clips (specified as URL, start, stop) as one dynamically assembled video with no user-visible buffering between clips.
Would this be feasible with the Clappr plugin architecture?
Sure. It seems that this feature fits well in a playback plugin. You can see some examples at our github repository. Regarding the concatenation of buffers you'll need to use Media Source Extensions API (http://html5-demos.appspot.com/static/media-source.html) but you should take care of the support of it on current browsers.
It seemed to us at the time that betting on an emerging framework and (what we thought would become) an emerging standard would result in something quite useful. What we ended up with was a very complex and fairly miserable project which was eventually replaced with something much, much simpler.