I recently found out that Hawaii has a unique "system" that they use for police cars. Many police cars in Hawaii are actually privately owned, so although they have "regular" American police cars, they have a random assortment of privately owned on patrol (Mustangs, Camaros, Mercedes, Audi, etc...).
I think it would be neat to have random "privately owned" police cars drive around as well. Maybe to make it more unique, give us players an opportunity to make one of our cars a police car. When their cars are active, they must have some of their lights on "steady burn," meaning their lights don't flash, they are just on. Maybe before we leave the garage, we can drive it around for fun or have the lights on "steady burn" and try to stop other players. Just a thought...
In terms of the use of sports cars as police cars in real life, most cars used were taken in on drug busts. However, there are some sports cars that were made specifically for law enforcement. Camaro's and Mustangs primarily were made with this package option. I don't know what Chevrolet called it, but Ford called it the "Special Service Package" (also known as "SSP"). There is a strong following of these cars as a hobby. Only reason I know is because I'm involved in it! Although I'm not in law enforcement, I've always enjoyed having the option to be on both ends in the game, both "the good" and "the bad!"
Just another idea... don't expect this one to make it in, but I'm sure there are others out there that will think it would be a great option!