seriously? Vader had already betrayed Starkiller, when he and Juno are talking after the rebel leaders are taken, Starkiller says that Imperial lives, credits, mean nothing to Vader, he just wanted the enemies of the Empire all in one place. Of course PROXY attacked when he did, to distract Vader and allow Starkiller as chance to escape, whether it be to run away, or fall off the damn cliff.
The infrastructure needed to clone a Jedi is another thing. It had to have been in place long before. cloning a force user can't be like cloning a soldier. He had to have intended to clone Starkiller all along. He didn't need the original any more, he just needed to have the Emporers enemies taken care of, then he would clone a perfect apprentice, and take control of the galaxy.