Ability to assingn nodes of one content type as children to only another

Hello, ronan.
At first, I'd like to honestly thank you - your amazing Node Hierarchy module really saved my project.

But there is one thing that is critically important for me.
For now, I can allow some content type to be parents and some - children. But I can't allow some content types to be children of only other content types I allow.
Say, for now content types "Model" and "Article" can equally be a child of "Car" and "Book Chapter". But I need to only allow "Article" be a child of "Book Chapter" and "Model" of "Car".

Please, include this ability to assign one content types as children of only another in next versions of Node Hierarchy.

P.S.: sorry for my broken english.