I know a few people have talked about using docker to package and distribute Galaxy tools. The most recent version now runs on all major linux distributions, so it's a bit more inclusive now (but there probably won't ever be a windows or mac version). One strategy would be for tool configs to define an option Docker archive name and possibly an alternate command line to execute if the docker archive is being used. 

How far has that work gotten, and what are people thinking about it? 

Kyle