It doesnt just have to be a few systems. More over time, gradually, would also work. There's not a lot between Disco now and what most action games are these days. The visuals are there, but the depth isn't.
There can also be more player input aside from events. Systems with nothing charted that gives players a chance to have an impact on that system. Nothing has to be on a grand scale.
Edit: And even if there isnt systems with uncharted anything, it gives the more eative minds in the team the freedom to let loose.