Operating system without installation media
I want to suggest to have operating systems without (or with optional) installation media, but with all the other goodies like partition- and provisioning templates etc. Use cases for this are PXE booted thin clients to access, for instance, Citrix, deployment of ESXi servers or info terminals. This devices usually load all their needed data via TFTP as part of the PXE boot, plus some configuration data (the partition- and provisioning templates).
At the moment installation media is mandatory. As a work-around I use a dummy media, which is rather clumsy and may cause trouble in later revisions of Foreman. Maybe the requested feature can be implemented as a new kind of operating system object.