How realistic is Elon Musk’s plan to launch the same Falcon 9 twice in one day?

Elon Musk has claimed in the past that the extremely quick 24-hour Falcon 9 reusey might happen in 2017 or 2018. This was yet another one of his overly optimistic statements, because two years later, SpaceX seems to be far from achieving such a feat. So I thought about what it would take to reuse a booster in one day, what it might look like and what is preventing it from happening.