I was thinking about two characters. It's been a long time since I took on more than one, that's my only concern. I don't think it would be a problem for me except for thinking up a good character for Columbia. I have time to think about my options though. 

I'm not sure about this idea but I thought about having a Little Sister that had the willpower and conscience of a rescued/cured Little Sister but still maintains the hunger and dependence of Adam, perhaps one of the early subjects to Tenenbaum's Rescue Little Sister plasmid. Kind of how Eleanor had side effects of her Little Sister days. The plasmid would have reversed the conditioning but left the slug intact.