Maybe they will consider genetic slots so players can pick things lactose intolerance. I sometimes wish they would create a new slot for a fatal flaw like The Sims Medieval had and made life much more complicated for the Sim when that flared up. It wasn't exactly 'fatal' but very much a flaw that made the player have to deal with it no matter what the flaw was and strongly affected mood and performance. Which I think TS4 could use some mood busters to lower their happyville lives. Once the fatal flaw kicked in (until solved) the Sim failed at almost anything it tried to do, such as romance, or quests, cooking, fishing, hunting, whatever it was the player needed or wanted them to do wasn't going to go as well as when the fatal flaw wasn't causing havoc for them. But I know other players don't want that sort of challenge so maybe a slot like fatal flaw could be something optional for those of us who don't mind Sims not being perfect.
