I still maintain that Medusa is a better option than Palutena because of her feel as a character, her role in the Kid Icarus series, and her ability to be unique compared to the rest of the roster. Saying she would never be added unless she was easy to add and would just be a semi-clone of Palutena is just as presumptuous and not necessarily even true as saying Palutena would only be in if she was easy to add, and would just be a semi-clone of Zelda. And you can say Uprising ruins her chances, but I don't think Skyward Sword ruins Ganondorf's chances of returning over Demise.
I honestly think Medusa and Palutena are competing far more closely for a place on the roster than 80% of people seem to want to even begin to admit.