But what I'd say on this is that I'd like Project Atomic to closely orbit the RPM ecosystem. For example, realistically you need content that goes into base images that gets reliable security updates.
Agreed 100%. This is one of the things that I did not see mentioned anywhere in CoreOS documentation - no mention of a packaging ecosystem used to manage image content. That's one of the reasons I am installing a copy on libvirt to see what the insides look like. Of course, I am also installing the F20 Atomic kvm machine.