[Jellby]

The problem is some of the desired features (left-right flow or top-bottom flow, touch to flip pages, navigation, and even maximize to screen size) are more a matter of the software displaying the book than of the book itself, and they're more user preferences (i.e. of the person reading the book) than design choices (of the person creating the book).

You can try to "reimplement" and "override" the reading software, but it it's a road full of frustration and incompatibilities, and prone to break with the next software update.

But if you settle for "show the images at the largest possible size, with no aspect ratio distortion", as phillipgessert says, that's doable and reasonable (except for the bit about not being possible to easily target the screen height, that's a true nuisance).