Provide an SDK for various languages to manipulate (at least read) a config
While I assume one can use the remote APIs to query the contents of a deployment (e.g. find instances), a programmatic interface to at least read the structure of a deployment configuration would be great to write custom tooling. E.g. something that would for instance do a rolling update of GCE instances with some custom health checks in between.
The ability to mutate the structure would be a great addition to this, for use cases where the provided update is insufficient (doesn't support the intended intermediate steps). E.g if adding a new local-ssd to an existing instance, the current update functionality fails. If I could read and mutate the config, it would be trivial to write some functionality to remove the instance first, deploy that, then add the disk, then deploy again.