I wonder how intelligently this handles piece download order. Torrent clients usually use rarest-first download algorithm, but if you've mounted a movie and you're playing it with VLC, you'd probably want it to download sequentially so there's as little time spent buffering as possible. You could download the pieces on demand (whatever piece the application is trying to read), but I suspect that will provide a suboptimal experience, especially if your download speed is barely above the bitrate of the movie.
I wrote https://github.com/anacrolix/torrent specifically to address the on-demand and streaming requirements of some products I created. It also doesn't make assumptions about how you store the data as you stream, so there's no requirement that the files exist on disk as they're described in the metainfo, like other clients.