We do even more, we take snapshots as the "Layerfile" runs - this basically lets you merge the memory dump semantics you mention with the interface of Docker.

We do even more, we take snapshots as the "Layerfile" runs - this basically lets you merge the memory dump semantics you mention with the interface of Docker. Also, we monitor which files are read by any step in the process, and let you skip setup chunks that don't need to run (i.e., installing libraries) without needing to micromanage what files you copy into the staging server.