I really like the constraint that you can't just take a detour to turn a "No" into a "Yes." It actually protects the consequences of the story.
When you hit a Pivot, do you prefer players to overturn the original question, or turn it into a whole new conflict for the scene?
I'm working on an interactive narrative right now, and I'm really drawn to design choices like this—ones that bring in genuine surprises without erasing the player's choices.