I wouldn't mind seeing more option for Sims' personalities like atraction system from TS2 or favourites from TS3. However, zodiac signs were always useless and meaningless for me in every iteration (which is pretty realistic, when I think about it). But that being said, I also like your idea :) I like that you came up with signs unique to the Sims world and conected them with toddlers' traits. I feel like they are less important, compared to the whole Sim's life, so you could easily direct your Sim the way you want later on. And maybe it could even change your mind and influence the story you have planned before :)