Clone a Game & add/modify more features

We need a game similar like GTA4 Something like this : - [login to view URL] So the hardest is to make a good engine for the police. More Details :- With GTA you have one-5 police cars. 5 is very much police and 1 is a little police. But yes, this is not very important and maybe will cost this much more money... You need to steal cars and there are as example 10 different cars. You can make this cars (as example Ford Mondeo, Fiat punto, Audi A6, Porsche 911). All cars need a picture for outgame use (around 150x80px). All cars can have damage, like in that game you send me. If you bring it to the garage, without taken by the police or 100% damage you will get an amount of money. This must not be very easy. You can bring 1 car per 10 minute to the garage as average. As extra option: You can kill pedestrians by shooting/boxing (what's the easiest to make?). And you can kill pedestrians by driving over them. When they have a portfolio this will put on the road. When you step from the car you can take it.