Adobe needs to simplify the placing of layered Photoshop files into Illustrator. You should be able to simply place a PSD file in Illustrator file and have the layer settings automatically apply just like the do in Photoshop. If a layer is "Normal or Myltiply" it should appear that way without having to convert layers to objects. That way you can simply make adjustments to an image in Photoshop. Then you could also link the files instead of having them imbedded.