WOAH. Now that's interesting! I may have just found my new preferred way to play Minecraft.
However, I wish hardcore mode would be implemented a bit differently. Instead of deleting the world upon death, the world should subsequently only be playable in ghost mode, where the world can still be played but the player can only fly around looking at things in like a God mode. The world can not be altered in any way, nothing more can be built or changed, and no blocks can be altered any more. Mobs wouldn't even see you or attack you, and the player would be able to even fly through walls and solid surfaces (since they can't open doors this would be necessary). This way you could still visit a world full of impressive things you had built and even visit the place of your death, but the world would be forever locked and done with for playing in. THAT would be awesome....