I think units should only have secondary weapons if they are programmed to automatically switch to that weapon where it is appropriate. There's some debate about whether AI cavalry currently do this enough in RTW. And the pike to sword switch in phalanxes was often infuriating. From a player's point of view, to have to micro manage the switch seems ahistorical (the lance is broken - what are they going to do? hit the enemy with stump?) and inefficient (if, as seems likely, the game plays at the same fast speed as RTW).