No matter what, they'll still be dampened by the overbearing emotion system. I think they could tweak the traits enough to give sims more of an identity. Here, I wrote a long tl;dr of what I want.
- Active: Get energized more frequently, autonomously engage in activities, grow bored when studying/reading unless they're also Bookworks or Geeks, or are Focused.
- Cheerful: More likely to talk to others, bad moonlets last for half the time they usually do. However, too many negative emotions will bring them down and make them last longer. Even cheerful people have bad days.
- Hot-Headed: More autonomous angry actions, the Feeling Angry moodlet becomes much stronger and lasts longer, and there are more triggers for it.
- Music Lover: The Frayed Nerves moodlet makes them lash out at sims who play their instruments poorly. They'll autonomously turn on the station and listen to their favorite music stations. They can autonomously sing or hum to music that's playing.
- Childish: Being lectured or yelled at makes them angry and actively avoid socializing with that person. They get a skill boost for Mischief and like pranks, but hate being pranked themselves. Work, homework and school projects bore them more often, and they hate doing chores. Teens and adults can socialize better with kids, and kids won't have a negative reaction when being lectured by them. (They know howto talk to kids.) Autonomously plays with toys.
- All the traits from Sims 3 get their Sims 3 effects. And also we get five trait slots instead of 3.
- There's now a Dragon-Lover trait
