You are making a lot of assumptions that would not hold true overall:
(1) That you wouldn't change your mind when you found yourself in that position. A healthy 25-year-old who says "I wouldn't want to live like that" isn't in possession of all the facts.
(2) That your children wouldn't want to hurry up their inheritance before it's "depleted" . . . they might decide they didn't want to waste money even on basic care . . . they might even falsify an affidavit when you are too drugged or sleepy to know what you're signing . . . and THEN you have a real problem, because there will be nobody to speak for you, once the general prohibition against murder is removed.
(3) That your doctor wouldn't want to hurry up your demise in order to get your hospital bed, or because your insurance limit had been reached. Another real problem, once the doctor has permission to kill.
Laws are not made for the good and altruistic, but for the evil and greedy. Once you give permission, people take advantage. It has already happened in the Netherlands.
May you never find yourself in that position.
AND in Florida.
AND in Florida.