This data type is coming quite close to release with full support for XPath filtering.
Here’s some screen shots with an example:
So the above basically will make sure that the editor cannot link to faqCategory or faq node types. Here’s the result in the editor:
As you can see in the editor these 2 node types are disabled and not clickable…. sweet!
The XPath filter support full xpath against the standard Umbraco XML for an individual node.