Johan shared a link for Cask with me. Look like an excellent and well needed tool for serious Emacs development. Serious being open to definition of course.
Dependency and software project management tools seem to slowly drift across language and system stacks, always being re-invented. The study of such systems, and the development of a singular and unified approach in the form of a library looks like a lot of fun and serious hard work, probably only worth pursuing if the result were a PhD.