It would be helpful to be able to change dynamically the properties (size, orientation) of a layout and map frame in a map series.
Dynamic properties could come from a field in index layer with value : portrait / landscape for orientation, A1-A2,A3,A4... for size (or size in millimeter, feet...).
It would be even better if we could define the position of each element according to the orientation of the page. For example, if layout orientation is landscape, title position is in X: 10mm Y: 200mm and if layout orientation is portrait, title position is in X:10mm Y: 280mm