A Reviews/Social Media tab in the managerial view that could show you guest reviews of your park, to add some flavor to your gameplay or help show you where your park is lacking. It would also add some much-needed personality to the guests, while not making them overly complex in the actual park as to avoid performance issues.
Messages like "This park is great, but there's nowhere to eat...", "The dinosaurs look a little bit sad...", "A gallimimus ate my watch, I want my money back.", "The dinosaurs are so cute!!!", would be really fun ways to both assist in challenge mode and add to gameplay.