You'll be glad to hear that I've already done something to that effect. There is now a 20% chance that the random encounter is against slave traders. They carry a different load-out than the usual bandits. I was thinking of adding a chance that a slave can be captured after a random encounter with the slave traders, but since there's only 18 of them it would have to be a slim chance.
And the Immortal Badasses will make an appearance as well, I'm thinking of giving them a 10% chance to appear at random encounters