If I understand it correctly, you're not pushing data from one device to the Chromecast. You're just telling the Chromecast where to stream the data from. One possible solution to this I think would be you'd have to have VLC setup a webserver that would stream the content to the Chromecast since Chromecast is essentially just a Chrome browser. So not impossible, but to do stuff like what you're asking for is probably not going to be completely trivial to do.
Someone please correct me if I have things mixed up.
Interesting. Thank you for posting that.