Wicket requires that a normal TSpace be rendered with additional interleaved objects that are not actually in the scene. These are what I call "ghost" objects. They are not in the TSpace hierarchy, but they can be rendered and used as if they were. They are actually owned by the TPortal in the case of the filters, which allows the programmer to render a scene with additional content when scene through the portal. What this means for Wicket is that the CAD tools, such as the 2D draw surfaces and edit boxes would only be displayed through the portal.
A related issue is removing objects in a scene. This tends to be a bit more complex, as it would require every frame to be checked to see if it matches a particular characteristic. This might be better done as some kind of global flag that the objects themselves can test against.