In the end it is up to the GM to balance the game and make it fun for all players, knights and swashbucklers alike. This does not even require any changing of the rules as the officialy stand. Armour may cost 0 CP, and it may be terribly effective in combat, but you can always let the enemy run away from the armoured knight, or make him trip and fall in the river or something; the swashbuckler would be able to swim to safety, the knight would have to be fished out (quickly). Or you can make a mixed group of opponents: some light types andsome heavy types so the knight would have to go after the heavy types and the swashbuckler after the light types.
You can just leave the rules alone and any theoretical imbalance among characters, after all, you are the GM and control the whole universe: balance the game by tweaking opponents and events.
