The real problem with static /dev is on the development side IMO -
managing the namespace of device names and major/minor numbers.
And that is the issue I think that Ron is reacting too.
One of the lines I have had about UNIX development is the number if namespaces its has. If you try to develop something like Single System Image Clusters (check out OpenSSI.org) you'll hit all of the namespaces.
Let me see how many I can remember quickly..
file system
per device inumbers for storage
device major numbers
per device minor numbers
pid
gid
sockets
port numbers within sockets per protocol
system V semaphores
system V shared memory
I'll stop here, you get the idea...
Ron is right managing the major/minor number externally which have internal meaning to the kernel can be quite an issue. Although, in fairness, it has worked amazing well for over 40 years. It was a simple solution and did not take take up a lot of space in the kernel to implement. I'm not sure for the PDP-11, I would have wanted much more. One might suggest it was pretty damned elegant for the time.