Also, the whole idea with Leia being Luke's identical "other half" is clearly a visual and symbolic play on the Jungian idea of the anima/animus--respectively, the latent "female" portion of a man's psyche and the "male" part of a woman's.
In Jungian psychology, attaining a healthy relationship with this buried "opposite" part of one's personality is a critical part of becoming a well-adjusted person.
Fitting with the gender inversion associated with Jung's anima/animus, the third draft's Luke Starkiller is naive and idealistic in ways that can easily be construed as feminine, whereas the strong-willed Princess Leia gets roughed up in a fashion befitting Clint Eastwood or Toshiro Mifune. The male lead is girlish and the female lead is a tomboy.
(This idea likely also explains Luke's shaggy haircut--in the second draft he had Flash Gordon-esque short hair.)
And in the rough draft, Leia's gang-rape is the catalyst for a symbolic and visual descent from Madonna to whore--a pervasive dichotomy concerning women in Western thought, famously identified by Sigmund Freud.
Obviously Lucas was reading up on Freudian and Jungian psychology from very early on, in an effort to invest his space film with some archetypal symbolism. Darth Vader as Oedipus complex, anyone?