Sounds like a good plan. I don't see why there should be any fear of controversy here--it's a standard replacement for the various ad hoc methods that were already in place. I was an early proponent and adopter of /lib/init/rw (replacing buggy use of /dev/shm as the tmpfs of choice for resolvconf), and /run will be a good replacement, which also cleans up the use of transient files stored under /var.
Reading the thread, there seemed to be good consensus on the need for /run, with one vocal individual disagreeing; however, the disagreement did not appear to address the fact that the existing FHS does not address the need for /run, and that standards are built on consensus, not set in stone. I'm sure that /run could be added to the FHS following its introduction. The FHS has not always established existing practice though--I'm still waiting for /libexec which both the BSDs and GNU coding standards have long supported, and it's a rather glaring incompatibility.
One thing I was going to mention was that LVM will no longer need to keep its cache files under /etc, which was a long-standing flaw in it, making a read-only rootfs easier to achieve. I subsequently found Alasdair Kergon's comments in the thread, which were nice to see. We could also get rid of /etc/mtab as well, without the need for a symlink to /proc/mounts before mount(8) is fully capable of operating without a writable mtab.
Is anyone working on supporting /run in Debian, and replacing /lib/init/rw?