Considering RCT3 pauses the game while the coaster editor is open and The Sims also pauses while you're building...and the fact my game has crashed twice while editing a building in play mode (although I have only 4.00 GB of RAM so I'm partly to blame here
), I think to have the game automatically pause when you're editing a building or building a coaster would be a great feature, as this will help the performance of the game and keep the FPS steady. 