Thirteenth Warrior did perfectly what it was trying to do, which is--in my estimation--a fine way to measure the worth of a film. It did worldbuilding and society in a way that few action movies even attempt. So, I'm going to agree with Skar and say it didn't, in my opinion, need any sort of improvement.
That doesn't mean, however, that a true-to-text working of Beowulf couldn't be extremely different from 13th Warrior and still be very good. As has been mentioned, the movies would be very different, including such things as supernatural elements.
I actually think the framework is there. Despite Beowulf's general lack of action (if you actually look at it closely, most of it is filled with people talking about great deeds) it could make a very interesting story.
And as for women warriors...well, the average woman placed against the average man would lose. Add equal amounts of training, skill, or talent to either one, and the woman will always lose.
However, there are other factors as well. Put an African man against a European man in a similar contest, and the European will usually lose as well. Place a taller man against a shorter man, and the tall man wins (because of reach.)
Warriors have to compensate for their shortcomings, and find places in the fighting where they can capitalize on strengths. For women, this probably isn't--as Skar has mentioned--going to be on the front lines.