There were a few things I really enjoyed about the miniatures game "Confrontation" from Rackham, before they really went downhill with pre-painted plastic miniatures, generally ignoring their fans, and going bankrupt. One was the elegant combat system, another was the way that certain character had specific storylines they could follow. These storylines typically consisted of three or more battle scenarios unique to the character. By engaging in these scenarios, a character could gain advantages and develop into a more advanced version of themselves. It blurred the line between rpg and miniatures battle-game in an interesting way.
I'm thinking about doing something similar for Ghost City Raiders.
In this case, all of the characters have a range of traits. The possession of specific traits will allow specific storyline quests to be followed. For example, a "nomad" might have a series of quests where they find plans for a new vehicle, gather parts and then build the vehicle. Engaging in the quest gives motivation and back-story to the events unfolding through the scenarios, completion of the full quest series would provide some kind of bonus beyond the normal scope of skills or attributes.
Still a general thought at this point. Needs more specific thought before I go further.