It would be nice if, for some host groups, I could check a box for the ENC to provide a fact containing all the hosts in this group.

Example usage:
All hosts in the CEPH group need to know about each other for CEPH configuration, firewall rules, and so on. I could pass the host list in as a parameter to the ceph class and the firewall class, or have foreman tell the host who is in the hostgroup and adjust my classes to use the value of that fact as the default.

This theoretically reduces the duplication of content while still allowing admins to override the parameter. As an optional setting of the hostgroup, it shouldn't have a performance impact if not enabled.