Add non-page content types to SharePoint Publishing Pages library

There are cases when you need to add content types that're not Page based to the Publishing Portal's Pages library. Such content types do not even show up in the Available Site Content Types list on the AddContentTypeToList.aspx page. Notice that there not many items in the listbox:

You can have any content types added to the Pages library, just not from the UI above. I recently worked on a project that requires a rather narrative professional profile page that has most of the columns of the Contact content type. So naturally, the Professional Profile content type should inherit from Contact. There is of course a custom page layout associated with the content type for displaying the content. The way to add the Professional Profile content type to the Pages library is to create a page with the custom page layout. The page layout apparently forces the content type onto the library:

1. In the Pages library, select New Document from the ribbon and then select Page to create a generic page
   
   




2. On the "Create Page" page next, select the Page Layout "Professional Profile", instead of the default (Article Page) Body only.
   





3. Once this page is created, the content type Professional Profile is on the library's content types now: