mtw 1 gave all units a wedge ability which was ideal so you could get your infantry through a gap in the line and swing around and charge the enemy in the rear.

wedge is best for formation maneuvring but only heavy cav get the option so i assume they intended it to be an offensive shock formation

i have noticed before that a group of 4 to 5 heavy cav in wedge commanded to strike a single infantry unit will wipe it out super quick. but you could probably do that in regular formation as well.

another tactic is to drive it into the enemies line and after impact command the cav unit to move beyond. this penetrates the formation and the widening wedge scores some kills as it passes through.