Just wanted to point out that both Apple (for iOS) and Google (for Android) have strongly discouraged the use of IMEI to identify devices for the purposes of application software. There are privacy, quality, and availability issues with their use. Apple has removed the ability of developers to work with the (often IMEI-derived) “Universal Device ID” (see http://blogs.avg.com/mobile-2/apple-ios-7-puts-unique-device-ids/) and Google has officially deprecated their use: http://android-developers.blogspot.ca/2011/03/identifying-app-installations.html
I’m not sure from reading the draft what the goal of having this URN namespace is, but if it involves encouraging its use by application developers, I’m pretty sure it’s a bad idea.