I've been scheming to insert Isaac Asimov into The Start of Eternity. The basic strategy is to assume that 1) Asimov was born into the Foundation Reality, 2) Asimov had a close encounter with aliens and learned about Eternity and the Foundations, 3) Asimov (and his memories) were protected during the reality change that destroyed the Foundation Reality and created the Final Reality (our Reality).
I previously suggested that Asimov wrote science fiction stories about Eternity and the Foundations by making use of memories that were transferred into his brain from a robot (see previous blog post). However, what if Asimov also received information about the distant past of the Foundation Reality, but was so disgusted with what he learned that he never wrote about that aspect of the Foundation Reality?
I'm thinking that during the time that the Asimov from the Foundation Reality is "between realities", he has a chance to interact with Hoosky and other crew members from the Many Sails. Asimov makes it known that he is a science fiction writer and someone suggests that he read "The Uvadekoto Saga", an account of the spaceship Uvadekoto and the first interstellar journeys of the Retair species. Thus, Chapters 10-13 of The Start of Eternity would be a "story within a story" that is read by Asimov. Asimov can be shown dismissing the saga as "bad science fiction" (and refusing to finish reading it), even though it is an actual account of historical events.