Edit overlapped objects
Some times when you use illustrator to edit PDF obtained from Cad programs, you get overlapped lines. It will be a good idea to have some filters to edit overlapped elements.
Miles Stevens commented
No experience with CAD files so I have no idea if this addresses your needs: suppose you have two overlapping elements—holding down cmd (on Mac) and clicking a top-level object allows you to select the object right underneath it. Sort of like clicking "through" the top object.