I think I like this idea too. Palpatine plays the father figure to Anakin, promoting him and encouraging him. Later, Anakin may test his 'father,' as all males tend to do, and Palpy may just throw some smack down and say, 'boy, I brought in into this world, sorta, and I can take you out!' Leaving Anakin in a state of dire medical attention, Palpy builds Anakin into Vader causing Vader to become dependant on Palpy. Then, we see in ESB that Vader is tired of being 2nd fiddle to this old guy with shocking fingers. He wants to rule the galaxy (decided what's best for them and make them do it) with his son. But, he still has to be Palpy's puppet while courting his son. Palpy already knows that as a sith lord, the apprentice will eventually (try to) usurp his master and take over. So, what better way to remain the master? Have someone kill your apprentice, then take him as your new apprentice. Simple. Except for that little thing Luke did.