It is a good idea to create a "realistic" medieval game, but there are several issues that you would have to address. First, basically that "realism" is never reality itself, and that there will always be distortions when the media, like games, tries to portray things. For example: did you know that Alexander the Great only lost 750 men due to battle injuries during his entire drive eastward? The media tends to romanticize medieval and classical combat, but in many cases, it was well-trained and armed soldiers fighting against rag-tag combatants. Alexander lost far more men fue to construction accidents and disease then he ever lost to the sword.
Second: As far as Medieval Europe is concerned, no one has any real idea of what the combat looked like. Almost all the writings on combat techniques have been lost, and martial training was largely kept as a secret handed down through families of the aristocracy. They felt it was something like a military secret to train people widely beyond basic blocks and strikes. A colleague of mine is actually involved in an effort to reconstruct German Zweihander combat techniques from some of the few books we have on the subject that have survived. Combat techniques did not have the importance then that we seems to place on them today, even Rene Descartes once wrote a book on the art of fencing, and no copies are known to survive today. Needless to say, if a famous philosopher like Descartes -who's books are often treasured- has works on the subject that did not survive, then there is little hope to find any medieval books from martial experts.
Third: Armor is not all it is cracked up to be. There are documented cases of British conscripts being lavishly armed at great expense, only to have them toss the armor away at the first opportunity before battle. Heavy Armor looks great sitting in the hall of your castle, and even better when you wear it. But it requires tremendous training and strength to use properly. Also, at least by the 1300s, armor became something of a show, portraying heraldry and religion rather than actually serving a purpose in combat. Really, most people taking part in the actual battles kept their own armor to a minimum, just enough to protect against arrows and glancing blows.
Still, it is an interesting idea, and would likely make a great game.
*edit, whoops I made a typo. Alexander lost about 700-750 men to battle in his drive east, not 75. Well, that is still really awesome. BTW, the source is Ardant du Picq in his "Battle Studies."
