Doesn't Linux create device files in userspace these days, anyway? I thought that's what that udev stuff was all about. So I'm not sure that the Plan9 workflow is inherently unfeasible, there's just no idiomatic support for it just yet.
device nodes are managed in userspace nowadays yes, but they're just special files that identify a particular device id pair and then the OS acts on them in a special way. udev is just the userspace part of things that manages adding and removing them in response to hotplug events. Everything that matters about them is still controlled by the kernel.
