The New Layout gallery cannot be customised, so metric countries and organisations see non-ISO layouts and vice-versa. This makes the gallery cluttered. It would be useful to hide the layouts that aren't required.
The second part of this idea is that there are two places in the ribbon interface to bring in a layout - New Layout (which includes Import Layout) and Import Layout. This is a bit confusing having two locations to add a layout. However the Import Layout gallery is customisable.
Ideally these two should be merged so that the New Layout and the Import Layout are in the same gallery and are fully customisable. But also keep the ability to choose another pagx to import if required.