OK, I might be in a minority here, but I would find it very weird to actually pause, say nothing and then come up with some ultra-structured approach.
If I were the interviewer, I would want to see whether the candidate can think on his / her feet and doesn't fall into "analysis paralysis" if a client throws you a curveball and asks an unexpected question.
So I would try to keep the conversation going, play for time a little bit and all the while trying to structure my thoughts. So applied to the specific question: "so what do you think is the impact of driverless cars?" my answer would be something like:
"Oh wow, that's a BIG question. Lots of places to start from." (Playing for time here but keeping the conversation going)
"I mean, there are the obvious 'first order effects' on the automotive value chain, the OEMs, the tier-1 and 2 suppliers, on urban transport, how people travel and commute. And then, of course, there will be completely new business models emerging, around transportation as a service for example." (showing that you have done your homework AND laying a trail of breadcrumbs for the interviewer to follow - you obviously only mention things you feel comfortable talking about)
"Beyond these first order effects there are a ton of less visible, but often very large, 'second order effects'. Take insurance, for example. Driver-less cars will have a lot fewer accidents, which in turn leads to much lower insurance premiums. So the car insurance industry will most likely contract" (show that you can structure and lay more bread crumbs)
"And then, if we look beyond the purely economic effects, we have a whole lot of ethical and societal questions to solve. I mean we've all heard these examples of the driver-less car needing to make choices between killing the driver or killing the pedestrian. And while these seem made-up and theoretical, it's just the law of large numbers that these things will happen at some point". (show that your horizon is broader than what business school taught you)
[PAUSE and wait for a queue on where to dive in. Pausing here will give the interviewer the chance to consider your answer and lead the conversation further. It will give you time to structure your thoughts, no matter what happens next.
RESIST the urge to keep talking to fill any silence that might occur. Really wait a few seconds, maybe 3-5. Many people, including partners in consulting firms, have a very hard time tolerating silence in a conversation for more than 1-2 seconds. Chances are, they are better at this game than you. if this happens and they wait it out, you can continue after a few seconds. In this case, you proceed from the top down.
But maybe, just maybe, your silence forces their hand and they give you a signal like "you mentioned insurance / urban transport / tier-1 suppliers. What do you see happening there?"
--> This is the breadcrumb trail at work. Go for that!
If they don't fall for that or just ask you to continue, you proceed from the top down, as mentioned.]
"As I mentioned, the automotive value will be impacted strongly by the move to driverless cars. For the OEMs, this means building entirely new capabilities, especially around software development and Machine-learning based technologies. They are obviously facing very different customer demands. Once we move to driver-less, transportation-as-a-service will really take off, like UBER on steroids. Once that happens, the demands of fleet operators operating fleets of driverless cars around maintenance, modularity etc. will be very relevant for OEMs, maybe even more relevant than end-user demands. And these changes will, of course, trickle down through the supplier value chain to the tier-1 and tier-2 suppliers,"
[And so on, and so on...]
I found that with this approach you can have a spirited, very convincing conversation with even only the most superficial grasp of what you're actually talking about. You can apply this approach to any industry where can do a bit more than spell its name. Try questions like
"What effect will AI have on the mining industry?"
"What do you think about over-the-top services like Netflix or youtube. How do they impact the entertainment value chain?"
And many more...