I think the most notable example here would be “day/night” shades like in this video (warning, sound).
These shades are designed so that there’s effectively two full-sized shades on the same window, controlled by the same device. Generally, one shade is a blackout shade and the other is a privacy shade, but there’s no standard as to which half is which.
The current structure of the cover component assumes that every cover will only have a single section. Since you can do half-and-half with these (e.g. open it to bottom half of the window covered by blackout shade, top half privacy), I’m not sure what the best way to include this functionality would be without seriously changing the cover services. The only practical thing I can think of would be to add an optional parameter to open_cover and close_cover for what section to use, and have those services default to opening/closing only the bottom shade if the parameter isn’t supplied.