Please see this thread. I don't think that your idea of the playlist for date added movies will work, as it doesn't work for anyone else and it appears that it is not important enough an issue to be worked on. If you do get it to work, can you share how you did it?
I don't know how you can say it's not an important enough issue. In the stock Movie Menu Item, I can click to the right and a sub-menu pops up which has recently added in the list (and movie icons also appear on the main menu for recently added.) Same goes to TV shows, right-click and choose recently added.
So If there was a filedate(or airdate tag) item in the list of all the criteria, I could easily display the last 10 item sotred by filedate in descending order.
I read the post in the link you gave. I guess I don't understand if it's already somethings that can be done in the stock install, why it can't be used to create a custom one.
<control type="button" id="90118">
I don't know enough about the xml files to be editing them directly..