Apple watch manual standalone mode for cellular watches

When going for a run with celluar Apple Watch, I will start to play music but it is streaming from my phone. I wish there was a way that you could tell your watch that you are about to leave your phone behind so that you could begin workout by using watch-stored music without it defaulting to use your phones library.

Also, when I leave my iPhone in the bedroom and I stand on the driveway before a run, siri becomes almost useless because the phone is too far away from the watch.... it has just enough bluetooth range to connect but at the same time it takes FOREVER to finish a command.

would be great if you could put it in standalone mode for times like this.