I don't know that any story needs a strong female presence. The Fellowship in the Lord of the Rings is entirely devoid of a female character, and this is part of what makes the Fellowship unique. If the book was written in modern times, we would have Morgan Freeman, Keira Knightley, and John Cho in the Fellowship, just to be on the safe side. If the story benefits from a female character, by all means include one. I have two female characters in my above synopsis, one of which is a temptress, the other being a more daring warrior who would probably play a large part in Episode 1, though I didn't get around to summarizing it here. The moment that I have to find something for them to do to justify their screen time is the moment that they being to drag down the story.