How to implement the 'Add Rancher EFS Stack' catalog service?

I’ve documented my struggles with the new rancher-efs service here: Convoy EFS to Rancher EFS

It isn’t that it doesn’t work for me; it actually works quite well and even, in some sense, more logically than convoy-efs did; it’s that the behavior of rancher-efs is so different from convoy-efs that you can’t really migrate from the older one to the new one and nothing exists that works like the old one. At the moment, we’re stumped on how to move some of our existing applications into Rancher 1.2.