To point out: this is the way it is today.
But if people have an aversion to this idea - and of course they would - then you could exclude life saving treatment from the queue and still improve quality of care.
I don't agree that this is the way it is today and that's because our system is rated to be quite a few places higher than the US system. If we want to have the best in the world then we need to strive for a system as good as the world's leader. That is far from the US example.
And so we can return to the question: What does a two-tier system provide to the very wealthy that can't be provided to the rest of the people?