With regards to Rey, whatever fanboy misgivings I may personally have about the writing, I do think its great that Kathleen K. and co. have given young girls their own Luke Skywalker to look up to and dress up as.
I’m in two minds about this, because to me it feels like putting the cart before the horse. I agree with the idea that these franchises could use a lot more female protagonists and antagonists, and that gender should not be a determining factor in casting a character in general. As such on average there should be about an equal number of male/female protagonists, and antagonists. However, I consider the statement, that young girls cannot relate to or identify with Luke Skywalker, because he’s male to be inherently sexist. The character of Luke Skywalker is an avatar for the desires and hopes of both men and women. As such, it shouldn’t matter, if the character is portrayed by a man or a woman. Lucas wasn’t trying to cater to a specific gender group when he created the character. Consequently, Luke could have been a girl, and the story would have played out in exactly the same way. The only time the gender of a character matters, is when that character, has specific traits, that are gender specific, or if you want to specifically relate to a specific gender group. In all other cases casting should be driven by having equal representation of men and women, not by the sexist notion, that men can only relate to men, and women only relate to women.