I feel that a relational database for charcters in an RPG would be a good augmentation to an overall emotive character state.
What I mean is that you store information about how different characters relate to each other, whether character A likes or hates or trusts or mis-trusts character B-Z.
Augmenting the relational view of characters as the player interacts with them, so that their actions have long lasting repercussions on future events and interactions (you insult a guy in the local tavern and the next day his brother, the blacksmith, won't shoe your horse).
You could also have characters with pre-dispositions towards other character races/sexes/classes (his family was killed by orcs, he kills orcs on sight).
In the end it's a twist on the mainstay of Zelda style RPG's....the puzzle...instead of solving how to find the flaming sword to open the mystic portal, you'll be solving how to chat up the barmaid in the local tavern so you can stay after hours and steal the barkeeps cash.
Emotions can also spike in different directions. Make a character frightened and they are more likely to run away, build a character's confidence and they'll follow into a suicidal battle. Instead of blind allegiance or oh-so-scripted responses you could have more lifelike and difficult to control characters. This could increase the gameplay aspect or destroy it depending on how it's implemented and the player market you're after.
Overall it could potentially give a lot more depth to a world but will, yet again, be another thing to tweak and tweak and tweak.
Mike