And this is all because we think the filesystem abstraction is the only way to go. NVRAM certainly could replace disks on some devices and really, what's the difference between storing data on disk in a filesystem and storing on disk in the form of pages?
There are many other, better ways to do IPC.
I don't think a filesystem-less Linux would work that well - the concept is too ingrained into the kernel. But starting from scratch? I would seriously consider not providing a filesystem at all.