Yes, I've been giving it more thought, and you're right. The offensive and defensive guards are not really needed in the system. The rules can simulate this already.
I am very curious about how to do the two weapon fighting, though.
Also, I use a variation of the initiative rules. Instead of rolling initiative before the fight, I do it whenever two combatants meet in close combat, and not before they do. Since combat in Ars Magica is very narrative, we describe how the combatants close in on eachother (if one wants to flee, we compare quickness and load). Then, when they cross blades (or axes, spears etc) we roll initaitve for these two. This makes it faster, and more exciting, I think.
E.