Actually the game wouldnt be that hard to make, if Rockstar ever wanted to use their software to make it, instead of doing Gang missions, you would normally start out in the firehouse, and thats also where you would have to ned up by bringing the ghosts back and all, and Janine would answer phone calls for you and give you directions to the place where th call came from, so janine would be the mission giver, so instead of alot of diff. missions Janine would always be the mission giver. SO you would hop into Ecto-1 or Ecto-1A, and use your map to drive to the mission area. And you would not be able to steal cars, because you wouldnt be able to get into other cars(see that makes it easier) instead you would have to get your Ecto repaired, just liek your car. After teh mission was over you would report back to teh firehouse and put the ghost in the containment unit, mission complete. But in ewach mission the ghosts get harder and harder leading up to the final climactic battle with Gozer or Vigo or soem original Ghost. SO teh game would be kind of boring and there would defrinatly have to be soem mini games and such in the whole game but it would be cool to see none the less, plus you could walk/run to teh mission place, just like the guys did soemtimes.
Send your ideas to Rockstar(who knwo maybe we'll get a game!),
Matt