"government seizure of private enterprise"?

There's no seizure occuring. Government routinely regulates the marketplace causing businesses engaged in that marketplace to have to adapt. Some prosper, some don't. Under a single-payer system there are still health insurance companies. They sell add-on insurance products, so there will still be private enterprise and profits in the health industry.  

And as far as government making investors whole if they suffer a loss, I think that defies the very essence of capitalism.