Sorry but thats actually wrong.
Read this:
This merely supports my hypothesis that neuron systems are what is needed... you will notice nobody is claiming that there are conscious people with 0% brain matter remaining.
You wrote this:
"We know people can have only 50% of a full brain"
And so the question is how you define a full brain.
Neuron systems are network. It might as well be that a network is needed not the neurons per se.
The line is arbitrary, but it doesn't matter so much. The factual reality is that neuron systems are what we can currently (currently! this may change) prove gives rise to consciousness, regardless of philosophical attempts at violence against the science.