You sure this didn't accidentally end up in the wrong thread? Not that I'd mind, but this comes a bit out of nowhere.
But making the lower castes viable and interesting has proven to be difficult under any rules system I've been dabling with. Nobles and warriors are easy, and outcasts living in the cracks of society also provide lots of hooks.
But regular farmhands and household servants? They just don't bring any special talents that would benefit in an adventurers life.
Just giving them lots of minor bonuses is one way to level the field a bit, but I always feel like that's a cheap solution. You still don't get anything that shines and causes rules bloat.