I think you are very correct, going by
http://en.wikipedia.org/wiki/International_Mobile_Equipment_Identity, but again, the device manufacturers must make it almost impossible to tamper with an IMEI, so that devices can be tracked using it.
What we really should be looking at is the tightening of the procedure for issuing SIM Cards, which unfortunately, would fall within the responsibilities of the MNPs. Most SIM cards are just being bought, used and discarded. Sadly, the crooks can easily afford a Mulika Mwizi, use it with such a SIM card and destroy it, leaving not-easy-to-trace tracks.
My thinking around this is still twisted. I still don't understand what a fake phone is. Perhaps those are phones that don't comply with certain standards and so expose the user to dangers of radiation, etc...