It would be really helpful if the Index page could have a separate field for recto and verso pages. At the moment, enWS has templates to do the logic (https://en.wikisource.org/wiki/Template:Recto-verso_header), but it's a bit non-obvious.

It might be easier and more obvious to have two header fields in the index page and simply use one or the other depending on the page number.

For wikis that don't want that, this would be set in the index page config JSON, so they can just leave it as it is.