When I create new OS every time I install fresh Foreman:

hammer os create .... --provisioning-templates "Kickstart default,Kickstart default finish,Kickstart default iPXE,Kickstart default PXELinux"

I need to manually set them in the GUI (Operatingsystem - Edit) because hammer os set-default-template only accepts IDs and it's clunky to use this subcommand.

We can automatically set templates if they are the only one of some kind, that won't hurt. It looks like a small change.

Note Katello already does its own auto-mapping, we would remove this once this is merged: https://github.com/Katello/katello/blob/master/app/models/katello/concerns/operatingsystem_extensions.rb#L14