Playing with alternate histories is — if you’ve already got the sort of mind that likes extrapolations and what-ifs — a great deal of fun, and it’s not surprising that science fiction and fantasy writers in particular (because they do have that sort of mind) have turned alternate-history into a viable subgenre all on its own. The fun of the game is muted somewhat when it’s played for money, however, because for the story to work the historical turning point has got to be one that a sufficiently large number of readers will recognize — which is why we’ve got “what if the South won the Civil War? novels by the cartload, but not a lot of “what if Mexico had never sold the Gadsden Purchase to the US?” stories, even though the resulting history of the American Southwest, and of Mexico, might have been a great deal different in a number of interesting ways.
I suspect that most writers who dabble in alternate history have got one or two “what-ifs” that they know will never make it commercially. My personal favorite:
What if Laurence Sterne’s Tristram Shandy, instead of being a weird outlier in the early history of the English novel, turned out to occupy the position of genre-prototype that in our history was filled by the works of Richardson and Fielding?
When I’m feeling particularly energetic, I can make a good-enough-for-fiction argument that Sterne’s interest in free-associative internal monologue, if allowed to influence the fiction of the next several generations, would have led to the development of psychology and psychiatry at least a century earlier than actually happened, and in a climate of Victorian optimism rather than turn-of-the-century anxiety. And when I’m really on a roll, I can argue that the earlier development of psychoanalysis would have done a great deal to alleviate Kaiser Wilhelm’s mental problems, especially his need to overcompensate for his physical inadequacies by building battleships. And thus, ultimately, Laurence Sterne would have prevented the Great War, and by extension World War II as well.
Of course, there’s no easy way to make a scenario like that into a novel, because for one thing, a depressingly large number of potential readers are going to say, “Tristram who?”, and for another, it’s hard to come up with the conflict necessary for a good story when you’ve got an alternate history that consists of a lot of unpleasant events not happening after all.