I imagine there are many ways to alter the overall story without the public knowing.
A stealthy assassination would do just that. A spy could gather intelligence on a location/target which may sway a battle. If you are skilled in disguises and forgery I imagine there is all kinds of tomfoolery you can get your hands into, to shape the path the story is going.
I almost feel like asking SBS to make triggers and things for the engine to wait for is doing the game a disservice.
We should write our own story and take it where we want. If the Devs want to trigger an event it should be something they dreamed up that is part of the story they want to tell.