With Arcpy.MP you are able to bring in .mapx and .pagx into your project using the importDocument() function. Once you run the function, the map and or layout is added to your project but the only way to access those again in your script is to do listLayouts() or listMaps() and find it using its name.
It would be incredibly useful if after running importDocument() it would return the maps and layouts that were brought into the project. The function currently returns nothing, but if it could return a layout or map object or even a list, then it would be easier to work with it later in the script. I'm not always going to know the exact name of the map or layout that gets imported into my project.