Kaodi
Legend
Core feminist issues in most industrial societies aren't easy to translate into the super powered slugfests of the superhero comics. They're fights over hearts and minds and for long term individual behavioral changes.
I think one thing you could perhaps try would be to literallize this quote from billd91: The heroes are approached by an NPC who can let them into the minds of other people in order to change them from the inside out, a la Inception. What is especially cool about this I think is this way you could add obstacles to be conquered via super strength, lightning speed and eye lasers without having your "heroes" beating the snot out of people in front of the cameras.
There are a ton of ideas you could draw from feminist literature. The only problem is that many of them are perhaps much too complex for a game. For instance, I am not exactly sure how I would handle a feminist super modelled on Susan Moller Okin's theory that feminism and cultural tolerance (of any kind) are incompatible, and could perhaps be caricatured in a super who was violently ultra-cultural imperialistic (though not a racist).