Actually, that's Alexa's Hornet 900. I suppose that means the answer to your question is yes....Alexa did that to a 919.
The thing you have to realize before attempting ANYTHING that guy did is that he spent a whole load of time and money to finish that bike. Don't attempt unless you're willing to do the same.
As near as I can tell, you need to weld the frame to properly attach the RR swingarm to the 919 because the "dogbone" won't attach to our frame. Alexa is on Hornet's Nest every once in a while, but his English is so-so (by his own admission). You can feel free to ask him about his mods. He's been pretty pleased to share his work.