>The only issue i see with that technique is that it prompts the user for participation and hence we are at their mercy.
BTW this is not true. I coded some scripts to ask the user for permission only to provide visibility that I was using a Service Worker. Normally a website would never ask for permission. I guarantee you that there are Service Workers registered on your computer from sites you visited. Surprise yourself and see what Service Workers your machine has acquired due to casual browing:
chrome://serviceworker-internals/
I have a dozen Service Workers registered on a machine I reformatted last night.