One way for everyone to get almost every car type they want in NL is to allow .3ds files to be imported as new train types. SM does this. It allows you to make your own trains and put them onto specific track types. I also think that instead of having 2 diffenent track types for the BM standup and BM sitdown etc., you should just be able to choose the car type you want for 1 track style.
I agree with that nannerdw, the multiple tracks is a waste as they use the same tracks for some, and 3d cars would open up both other ride types and innovative new train types. Also, I think each track should have more specific options, such as different rail amounts for intamins and the loop type track with the big midrail for schwarzkopfs, etc.