I would say that they didn't say that you have to be competent at the time of the provision of assistance. That is unclear in Carter, so it needs to be set by you.
I would say no to substitute decision-makers. I don't know that anybody is advocating for that. I would also say that advance directives of the sort proposed are not inconsistent with Carter. If you look at the trial definition of voluntary euthanasia, it includes “in advance”.