It's a lovely idea in theory but really, think of the command, control and logistics.
It works as paliative care but goodness me, I don't want to be stuck on a windy rooftop should I take a turn for the worse. Maybe they only take them up there for a bit of a breather and take'em back down again later.
Perhaps I've misunderstood the article but open air critical care on a rooftop with heavy traffic going around is generally known to the unwashed masses as, "Refugee Camp" or, "Warzone Situation."
I do not expect to be holding down my heart monitor with one foot against the stiff Thames Estuary breeze whilst my immunocompromised self gets hayfever from Happy Clappy'sflowery things and carries me off, once and for all.
Apart from that. It's great.