Would love to see 1) a horizontal scrolling option (aware of UX/interaction cost considerations) but this could be really useful for extra content outside the viewport as long as it's clearly signposted and controlled as per vertical scroll motion. Currently can only achieve this through some hard CSS coding/testing to get right.
2) Probably of more widespread/immediate use would be a horizontal scrolling gallery image/video option controlled via scrollbar/arrows (this functionality is pretty much there in the media gallery option when you click on an image/video to then go through the exploded slideshow, so shouldn't be too much of a jump to have it as a main option).