I got further in embedding the actual NetBeans HTML Editor into a multiview window:

Since the above is the actual HTML Editor used in NetBeans IDE, its features are registered in the layer files of the modules that provide those features. Hence, since the NetBeans HTML Editor provides many features that are not relevant to files in the MemoryFileSystem, such as the one shown in the document above, removing those features is as easy as masking them out in the layer file. For example, I removed the whole popup menu (since everything in there is irrelevant to the above scenario), together with some of the actions in the toolbar, by adding this to a layer file:
Still buggy and not complete, but here's all the code that produces the above application: MyCMSSystem-alpha2.zip

Read More about [NetBeans HTML Editor in a Multiview Component...