This won't help you if your internet connection is down.

With source code escrow of their services, you can presumably use dns redirection of their site and the open source version of their software to run your own local instance of the stack.

Truly Open Source doesn't mean runs without any other components, it just means you can replace any of the components yourself.

Sure it will. GCE just runs containers.

That's a good idea in theory, but what about maintenance and related devops? It's not enough to assume the code would be reliable on its own.

What kind of organization would provide this service? And who pays for the infrastructure?