Thanks for the ideas, but I don’t think your features should be inside a protocol. A protocol ist actually nothing more than a contract that some service might fullfill.
Most of the features you request are actually services and can be done with more or less effort even with the todays version of the hermes protocol. For example media streaming:
You can listen to the intent, take over the control of the session and start your own exec-command with using any media player. I have done the most of these things with using NodeRed for the flow control. Works smooth.
But some features like the dockerization of snips would be a great feature indeed. Keep on going