We have hierarchical acls. Those enable us to set on a item rights which will be used on all children (subitems) of that page unless new acls set.
This hierarchical concept should not only be used for acls. It would be nice to force the contentype by this unless it is changed for childrens (subitems) too. So you could for example define all subitem of the item Images are only images and may be only jpeg images. Or all subitems of a plain text item are also have to be plain text.