I know that since Madoka is the main character, she had to be Luke, and since Kyoko is Han, Sayaka had to be Leia, but I genuinely think switching Madoka and Sayaka would have ben a good thing, leading to "non-conventional" things.
I mean, Sayaka already wields a saber and is Madokami's knight, so from a certain point of view, she was fit to wield a lightsaber and become a Jedi knight. Plus, her battling with Darth Homu would be a nice throwback to Rebellion and to another SW/PMMMM crossover fanart.
Also, a pairing like daring Kyouko/shy Madoka can be quite interesting.
Now, for something completely different, I really like that Tatsuya Shingyouji thought of 3PO's silver leg from the first film.