Please don't do it. If accuracy is not important, why not work on oriental/middle eastern weapons and armor? There are a ton of things you could be doing to improve the game besides implementing female character; new maps, game mode, dev tools, etc.
I personally think it would be more realistic to add magic to the game. Woman have no place on the frontline of a realistic medieval battlefield. It will destroy the feel of the game.
fiction vs fantasy
fantasy = magic in the medieval era, it is something that has no basis in reality and is not plausible or within the realm of being possible
fiction = female soldiers in the medieval era; there were female human beings in the medieval era, that have hands which are able of picking a sword up and swinging it around. this falls within the realms of being possible and is plausible