Layers in PDF files are different than layers in Illustrator or Photoshop. That's the reason that there is no direct way to import a layered PDF into Illustrator.
What you suggest would be possible in a custom plug-in, if you are interested in having something like this developed, feel free to get in touch with me via email.
Karl Heinz Kremer
PDF Acrobatics Without a Net
PDF Software Development, Training and More...
http://www.khkonsulting.com