Cool idea ! One useful feature I can think of would be some kind of flowcharting functions so you can organize your story flow with perhaps optional conversion from the flowchart to a basic layout. Then the user could add stuff to the layout like images and audio, edit the hotspots the way they want and so on.

There is a built in navigation tool that keep track of all pages and how they are linked together.

The way you can look at the program UI wise, is that you have a work area, which is just your whole screen and would be one page, and you can add whatever you want to this and move it around where you think it should be. This also include hotspots, which I call triggers, which could be an image for instant and you can move this where ever you want it to be and it would only interact there, for example if the viewer clicked it.

All objects (Videos, images, triggers, texts, progress bars and so forth) can be dragged around with the mouse.

So each time you add a new page you get a clean work area where you can built the next part of the story.