Actually, why isn't this a good idea? If it was understood that the default treatment assumption was Do Not Resuscitate/Intubate and you had to consciously opt-in to a different standard by providing a living will or offering written instructions at an earlier date, wouldn't that be better for everyone? There's no cost to claiming a different code status, but there's a huge cost, currently, when we assume the maximum. This would seem a more logical system all around.
For that matter, I also think folks should be considered organ donors unless they opt-out or their descendants raise post-death objections. We should err on the side of positive social outcomes, not huge spending and wasted organs (which translate into more wasted lives).