Could you elaborate what alternatives to docker are worth checking out? I'm unfamiliar with containers and out of my head I can't name anything besides docker.
The lesson of Linux is that fragmentation is bad. This is a chance to fight fragmentation.
rkt is likely going to be replacing Docker for the default engine in Kubernetes and/or OpenShift (I vaguely recall hearing that it was coming, but can't find a source to cite): https://coreos.com/rkt/