What about human-emotion simulation as well?
After all you can't exactly like everything as well as dislike everything about someone. Some survivor may argue, some may cheer or have fun, some may have lovey-dovey like kissing, hugging.
Also make the tendency of the "Working" animations tied with the morale, higher morale means that they are most likely to perform personal animations or just laze around. Lower morale indicates that there work still needed to be done, thus "Working" animations are played much more frequently.
An interesting suggestion indeed! I dont know if it's gonna be easy or even possible to implement, but the idea is very tempting!