You could always have a script which strips down things to only necessary configuration values for production and then generates a tarball that could be verifie

You could always have a script which strips down things to only necessary configuration values for production and then generates a tarball that could be verified. It seems like it would be possible to get down to a subset of settings that could take on any value while still allowing you to trust the service. Of course, if the settings don't have to be secret, they could also just be baked in as well.