What's described in that doc is even easier today thanks to Operators (https://coreos.com/operators), which, to quote the description page, are "application-specific controller[s] that extend[s] the Kubernetes API to create, configure and manage instances of complex stateful applications on behalf of a Kubernetes user."
Disclosure: I work on Kubernetes at Google (and wrote the doc you linked to).
The limitation of only being able to run Containers I think will be fleeting — as docker and alternatives mature, it really won't make sense to ever use anything else when trying to get the scale that Kubernetes and Mesos is going for by abstracting out the underlying hardware and providing a framework to run sophisticated apps on undifferentiated hardware.