Blendability is certainly an worthy objective.
However, I'm not sure that we'll take you up on this one any time soon. It's a matter of best use of our resources.
If I thought people should use these views in an application, I might reconsider. But my sense is that the Model Explorer XAML is really besides the point and not terribly useful in a real app. Moreover, Blend (like all such tools) has a tendency to inject a lot of ... what's the word for it? ... let's just say distracting and superfluous XAML. I'm afraid its contributions might obscure the (already limited) readability of the XAML.
Tell me I'm wrong. :-) Ward.