I highly doubt he thought Force lightning could deform somebody at the time of ROTJ, going by the example of Luke. Also, we don't even know that he thought that by the time of ROTS either. In the first draft of ROTS, Palpatine says he was the one who created Anakin. So that was apparently Lucas' plan around 2003 or so. Anakin being the Force's response to Plagueis did not appear until the Plagueis novel, and as far as I know we do not have information saying that was a particular choice made by Lucas himself. ( Even then Anakin is supposed to be a response to Plagueis and Sidious shifting the balance, not the cheating death thing. ) What exactly is wrong with his own interpretation?