No, _you_ think it's a bad idea. Many people have wanted devfs
for a very long time. It has been coded up twice, including a
recent reincarnation as "SystemFS". It is in FreeBSD, Solaris,
and AIX. Linux wouldn't be alone at all.
All problems can be solved. FreeBSD uses an invisible filesystem
that only the kernel can change. When you mount the filesystem,
you get something like a copy-on-write version of it. Solaris
seems to use tmpfs and loopback mounts, assisted by some shell
scripts. SystemFS uses a daemon to keep everything together.
As far as I can tell from a quick look, changes you make to /dev
get reported to the daemon for long-term non-volatile storage.