Thanks Ken! I'll go with the overlay way for now.
On the other hand, I was experimenting the embedder service last week, there were bunch of issues I encountered with (mostly how to do X), off the top of my head:
I need to have WebView service under content packaged services, otherwise it will throw me an error message.
It seems we are deprecating service_manifest gn template, but I didn't see an alternative way for that.
I feel both are documentation issues though, hope my feedback could give some ideas.