I would love for it to be possible for Hearthlings to form relationships and have children. The process of that would be far less graphic than one might think, perhaps it looks similar to a Sims woo-hoo sort of thing. Children could then attend schools, which one could possibly assign, to change their body, spirit, and mind stats with minor one or two point increases. Then, maybe after fifteen or twenty days, they grow up and can function as workers or other professions.
Perhaps even serve as apprentices for the crafters.