Perhaps the very reasonable principle that 'we must preserve life at all costs' (and I don't mean money costs, particularly) is all very fine when our means of preserving life are primitive and uncertain. It is a very different matter now that we can often keep life going in a body that has no meaningful living present or future. Modern know-how now means that we can condemn people to live - and I think we should not regard it as right to do so.
Of course there are problems of law - especially the problem of how to guard against abuse of power in these matters but that is the business of law in many other matters too.
I hope that we can consider this without recourse to the tired old phrase 'playing God'. Of course, my being an atheist, this phrase cuts no ice with me but it ought to cut no ice with believers either. Surely they can see that, in their terms, deciding to keep the switch on, against nature and common sense, is just as much 'playing god' as is deciding to switch off in the name of common sense. "Is my religion against common sense?" is a question believers should ask themselves perhaps more often than they do.
Please, I do not wish to be condemned to life by people who refuse to recognise what time it is and what degrading futilities our life-support technology now tempts us to practise. I do not volunteer to be a vegetable merely for the sake of other people's principles. I would prefer the dignity of a good death in accordance with my own.