I used to work on buildpacks -- can I suggest getting in touch with the Cloud Foundry Buildpacks team? They also do a lot of work around the Ubuntu base image (cflinuxfs2) and there's been work towards cflinuxfs3.

They also used to use soft-forked Heroku buildpack code. Almost all of the Cloud Foundry buildpacks have now been rewritten on top of a single shared library. The strength of Heroku's code was that each buildpack has a maintainer familiar with the relevant ecosystem. The weakness was that they were all different. Often forked from a previous one and then tinkered into submission.