Regarding 2: Is there any fundamental reason why full compatibility will never work?
2 - As Docker, Open Containers and other related technologies evolve the difference between system and application containers gets slimmer over the time. As an example well known issue with memory limits https://jelastic.com/blog/java-and-memory-limits-in-containe... now can be solved with help of lxcfs https://medium.com/@Alibaba_Cloud/kubernetes-demystified-usi.... I hope at some point we will be able to use benefits of both in one container engine.
2 - As Docker, Open Containers and other related technologies evolve the difference between system and application containers gets slimmer over the time. As an example well known issue with memory limits https://jelastic.com/blog/java-and-memory-limits-in-containe... now can be solved with help of lxcfs https://medium.com/@Alibaba_Cloud/kubernetes-demystified-usi.... I hope at some point we will be able to use benefits of both in one container engine.