If someone is capable of expressing their wishes in a tangible medium and fails to do so, how serious can they be about having those wishes carried out?
A requirement that required all advance directives to be transcribed in tangible media, period, could impose an undue burden on people who were unable to thus record their wishes, but it would not seem to impose much burden on those who were able to. Explain, therefore, why you would think it unreasonable to require that anyone who is capable of transcribing their wishes in a tangible medium must do so for them to be carried out.
1) If oral is acceptable (ie., meets your criteria 1,2&4), then why even bother?
2) Grampa, worth $20 million, writes on a scrap of paper that he wants to live no matter what the cost. How long would it take the family's attorney, being paid 30%, to invalidate it? 10 minutes?
That's two off the top of my head -- but the best two.