We went a similar but different direction in Canada, rather than killing the phone there's a list of IMEIs for stolen phones, and all carriers will honour not allowing phones in the database on to their networks. Which this solution sounds little less onerous than re-engineering every handset OS to have this kill ability.
I agree that this would be a great solution, but even just this will meet great resistance from the companies that profit from activating stolen phones. Cricket is one example. After having my phone stolen, I was happy that Sprint blacklisted the phone... then I did a little research and discovered that thieves need only "flash it to Cricket" and then they can use it on Sprint's network. I have a feeling that a large portion of Cricket's business comes from activating stolen phones. Expect push back on this type of law from Cricket and other similar companies.