Just do it like Sims 2 in my opinion it was just enough to be ok for teens and adults. I miss the connections the sims had with one another in that game. Parents with children dancing on their feet. The cuddle while sleeping for couples along with waking up in the arms of their significant other. Toddlers playing miss Mary Mack and fighting over bottles.
I often think it is less about making the game more adultish and more about the sims themselves making more meaningful relationships and expressing those feelings in animations and less in moodlets.
