Re: "self-driving systems can be considered a driver"
If the owner/"driver" doesn't have any control over the car other than giving it a destination, I don't see how they can have any liability for accidents the car gets into. A gun is a TOTALLY different thing, because someone has to load it, point it and pull the trigger, it doesn't do those things itself. It is a dangerous weapon, designed to kill, and leaving it accessible to say your small child who can't realize the consequences of using it leaves one clearly culpable in a way that telling your car "take me to the grocery store" does not.
So in the long run, liability insurance will be provided by the manufacturer, or some sort of "group" policy that covers many cars of the same class that people will pay for one way or another (even if the manufacturer provides it, you still pay for as part of the sales price) There is no way they'll hold individuals responsible for what their car does, any more than you are held responsible for paying credit card charges made by a thief who stole your card number off a merchant's POS system.
There will be a transition though, because autonomous cars aren't going to be introduced able to drive everywhere without human help or the possibility of human intervention. That's where legislation will be needed, to figure out how to handle insurance when the software can only handle certain driving tasks (i.e. expressway) but not everything so the owner must drive at times.
I think it is likely that once insurance companies are able to establish relative losses between autonomous and self driven miles, as autonomous miles get safer and safer relative to self driven, that driving yourself, especially by choice versus being forced to by the car being unable to handle certain conditions (i.e. gravel road in fresh snow) will quickly be priced out by rising premiums.