So this is actually not needed, as this is already possible with:

a) On katello server:

  node-certs-generate  --katello-org="ACME_Corporation" --child-fqdn="node.evel"  --katello-user='admin' --katello-password='admin'

b) On new node:


subscription-manager register --org "ACME_Corporation" --activationkey node-installer

 node-install --parent-fqdn master.example.com


I will update the documentation in the node-installer git repo with this tip.

small omission: 

command in a)  should have
     --katello-activation-key="node-installer"
on the end

@justin yes, if the --katello-activation-key is not provided, it does not create it. Also, other params for the repos with certs are available. see --help for more