I like the ghost idea, but don't like the 20 second idea at all. I think the spawning is pretty good right now, because it brings you to the speed you were when you were racing before. The game gives you about 5 seconds to look at the ghosted car that is about to spawn to give you time to get away with it, or hit it. Up to you!
But the ghosting thing... great idea! I'd like to see this happen.