Most people are scared to answer that question. In fact, they’re down right superstitious about even hearing the question.
Those who do answer the question tend to say either: (a) I would smite so and so, or (b) I would create world peace. Smiting a bad guy is easy. Creating world peace is easier said than done because there are too many variables involved for a mere human to deal with.
Okay, here’s where you find out that’s a trick question.
Those who aren’t writers often say that within any given novel, the author is a god. S/he can smite everyone who needs smiting and decree world peace without having to worry about the mechanics of it.
There are risks of acting too God like while writing a novel or a short story. Presumably, God (Himself and/or Herself) doesn’t have to worry about bad press whenever He or She manifests and Act of God. Human beings, being what they are, tend to believe that if an Act of God occurs and it’s bad, it must be their fault. They sinned, and so an Act of God paid them back.
If a writer puts an Act of God into his/her story, chances are nobody will believe it and the author will be paid back with a slew of one-star reviews on Amazon, and God help him or her if the book sells well enough to attract the attention of critics who will say, “The book was a wondrous sweeping saga until the last chapter when the good guys were trapped and suddenly–without warning or proper foreshadowing–a tsunami kills all the bad guys.”
Critics and readers alike will say, “I hate it when that happens.”
Basically, critics and readers don’t want the author to play God as s/he writes because the resulting story is unsatisfying, outside the reality of the novel, an example of the author writing himself/herself into a hole and cheating to get out of it, and other nasty criticisms.
Readers, frankly, are never willing to say that the author moves in mysterious ways and let it go at that. Authors who move in mysterious ways are variously bad, experimental, sinful, crazy, or tetched. Critics and readers typically want more order than authors want. They want the books they read to be safe and to fit within the world as they see it.
The bottom line is, the author can’t play God and has to let the story unfold however it unfolds. If you–as the author–step in and take any action whatsoever, it has to be sneaky and impossible for critics and readers to detect.
So, the author’s answer to the question “If you were God, what would you do next?” is “Little to nothing.”
That’s the reality of being an author. You have the power, but you can’t use it.