Ability to freeze actions
It would be nice to be able to "freeze" actions before I simulate my prototype for testing. For example, I often use popup modals in my prototypes, that I keep hidden until the user clicks on the button to launch the popup. I keep them hidden using "On Page Load Hide All" type rule so it would be nice to freeze that rule so the modal is automatically displayed when I simulate.
Another example where this would be helpful is if you are debugging to see why some weird behavior is happening in your prototype, you could rule out actions by freezing them and retesting.