Except, as was pointed out when this was last discussed, a blade breaks and stabs you in the chest. Every other flying vehicle with propellers has strict regulations against humans ever being in the same plane as the spinning props, so I'm not sure how this design can be made safe.
I would be less worried about the blade fragments stabbing me than I would be about tumbling into the ground at high speed if a blade breaks. That is a bigger safety concern here. With loss of one corner, you are a tumbling rock.
