In addition to the rides, scenery, shops, etc. One of the most important pieces of a theme park is the behind the scenes items which would add to the "Park Management" experience. None of the previous titles in this genre have touched on this aspect of the simulation and if PC were to incorporate this, it would instantly set them far apart from any of the past iterations and current competitors. It would reach a whole new level of realism "Simulation".
This could bring in for coasters, new levels of servicing on Coasters. A single train could develop an issue which would have to go off into the storage building for maintenance. This in turn would reduce capacity for the ride and increase queue times due to less trains running on the track. There are so many other areas that a behind the scenes items would add to the game outside of just coasters.