For us people that doesn’t only work in webs or touch based apps, but also in TV apps, It would be great to add functionality on the prototyping area that helps us try our designs.
The more basic one (but really helpful) would be to be able to assign keyboard keys to prototyping actions (Jumping to another artboard, show an overlay, etc.)
The most complicated stuff would require to be able to define focused and unfocused states in the screens and define links between those states to simulate a complete focus based navigation.