Thank you Alex for the advice. I looked it over and I think I was able to grab your boilerplate when it was well enough down the road that the new LearnR child theme gets all the important inheritances from Boost Union.
I sent this in an email to Wiebke, but I'll post it here too:
Boost Union is an awesome theme. It is so much more than just colors and styles. It changes the functionality of Moodle to benefit users and adds features and functionality that help aid in the process of delivering content and using Moodle. I am very happy for the work done to provide a template for creating a child theme. Boost Union is a true gem in the Moodle community.
Thank you for the hard work put into Boost Union by all the organizations.