The thing to keep in mind with parent worldspaces is that the child will be using the LOD data generated from the parent. This system is almost entirely focused on making the walled off cities work, and may not be practical in any applications which are particularly different. If I remember correctly the one thing it does have going for it is that the terrain within the child will be in the same position as it is in the parent, allowing you to duplicate features. If correct, this would allow you to parent a worldspace temporarily to get this duplicate terrain in some spots, but remove the parent link to be able to have a different LOD or make changes to those cells to blend it with other landscape. But again, the applications for something like this are rather limited.