As far as I read it, you are wrong about CoreOS. It's meant to be run as a host OS, not as a guest. It provides a minimal Linux Hypervisor you can use to run containers built for docker.
Yes, CoreOS wants to be a host OS, but it's also a ripping good guest OS, because of its minimalism. I'm expecting most people to basically stick their app and nothing else (like, say, a full ubuntu environment) inside of the container.
Hypervisor is the wrong word- that's what you'd call Xen, VMWare ESX or the host KVM kernel.
