Historically the cavalry were the offensive troops so it makes sense to me anyway that the Heavy Cavalry needs to be in the offense. To protect the Castle (villa) then some extra strong defenses need to be in place such as Strong troopers ( Halberdier,) Heavy Crossbow, Cannon etc. and a quicker...
My suggestion is to take the Heavy Cavalry trooper from the defence and make him the highest ranking offensive trooper. Then add a high ranking trooper such as a Halberdier or Heavy Crossbow on Defence to counter the heavy cavalry. This would give 4 different troopers on both defence and...