I think the important thing is that it's a form of deceit. It's not about the value to the public vs the value of the person's wishes: if you don't intend to go through with the wishes or believe there is a good chance that you will not be able to, then you should recuse yourself at the point of the request (or as soon as you realise). Deciding to stay involved and make your own choice is simply duplicitious - it completely defeats the point of having the legal power. It wouldn't surprise me if someone could sue the executor, since they are clearly acting against the best interests of the person.