add more options for slides and especially video slides.
give layout options like the size and placement of text areas,
pixel-based control of line thickness
better support for mobile and less mobile bugs
custom background images/thumbnails for videos
or even a simple list of the CSS classes to help us easily customize it.
if you made them easier to customize, even at a code level, I'd love this product, instead of it being an example of an itch almost scratched