In my opinion the isolation mechanism of major container software like docker is flawed and thinking about it gives me headaches. One problem is that you need a daemon running as root. It's better if you don't have to leave the user space at all. To be fair plash relies on fuse and newuidmap/newgidmap which are suid, so there is at least a little bit happening with root access rights. But it's comparably very little and there is nothing self-baked running as root.
There are many details that for me are unclear in docker, one out of the of the tip of my head, is that the usage of a overlay mount is disabled by non-root users (also inside user maps) because the kernel does not want to guarantee that a bogus setup can cause a security issue.
> Would you move to Docker/runC?
Never :-) The whole point of this is to not use Docker/runC. One of the core aspects of plash is that containers should just be normal processes. Processes is an interface that existed since decades, for containers I need to learn a new tool just to kill one or list all that are running (use ps/kill in plash)