Here's a suggestion I thought I'd toss out there:
Make other parties camp for the night the same way the player can. That way when you stumble on a camp you can ambush them (you'd enter it the same way you enter a town - get the options "Speak with party commander," "Ambush" or "Leave.") Ambushing would lose you a bit of honor but you'd only have to fight a fraction of the army's size, and would have more prisoners (maybe code it so most of the army are counted as unconscious - they're still asleep, after all). Success in ambush/party size you have to fight would depend on skills like Pathfinding and Tactics.