I only used Karl Franz in one way when I played my Empire (looking to rebuild it from scratch). I simply stuck him on a Barded Warhorse w/Ghal Marz and stuck him with a unit of either 12x IC Knights w/Lances, Shields, and a Mounted WP, or one of my personal favorites, I stick him with a unit of 28x IC Knights w/Lances, Shields and a WP as well in a 10x3 Horde Cavalry formation =D. Both are good options as it gives me a hard hitting unit, as I feel that Greatswords are a waste of points as they die to easily and just aren't worth it.