Development shouldn't end at marriage. There should be extra heart events for the married life. It would be really interesting to be able to unlock events that directly affect the marriage based on your answers. Wouldn't it be wild if your spouse could leave you because you answered poorly on too many heart events. I think conflict and consequences would really spice up the game.
Heck, I'd be content with there being an event where you actually speak to your spouse about having a child! Not the whole "Do you want to have/adopt a baby?" on a black screen where you can choose yes or no.
Personally, I'd settle for having a "holiday" on the calendar for your anniversary and special dialogue with your spouse on that day. Maybe a romantic get-away in-game event on the anniversary.