Linked Artboards as facing pages and folds
It would be great if artboards could be linked together as pages, to allow for automatic movement when one is resized.
Example:

That is a book cover, made with best practices in mind, in Indesign. Technically it's the same as a 5 fold brochure.
the background image can be attached to any page/artboard, right-aligned with autofit. If the spine is adjusted every page remains the same, except for the background which now shows more or less art depending if the spine was shrinked or enlarged.
Spine adjustments are important because they are re-adjusted every time the book is sent to print. Since the spine varies sizes depending not only on the number of pages but also the paper type, it's thickness, and other factors tied to the place where it will be printed.
Scribus can't make 5 folds (4 is the maximum), and the PDFs it exports are not fully compliant with the PDF X1A 2001 standard, meaning some professional users might be forced back to Adobe.