I have a couple of Scalextric Pacer systems I have used in the past. For those unfamiliar, they were an analog device that recorded a lap and then played it back, with an adjustable speed control. Given their limitations (10sec max lap, one re-sync point per lap) they still provide a decent competitor. It's necessary to drive a smooth lap (driving hard in/out of corners is bad as getting slightly out of sync will cause a crash), but when you finally get a lap that works it can provide fairly stiff competition. It's easy to stay ahead of it, but one mistake and you're playing catch-up the rest of the race.
Having used the Pacers, I'm sure with multiple sync points per lap a very good competitor could be produced. Sure, it will still not work as well for laps driven on the edge of control, but I have no doubt one could record a smooth lap that would handily beat a constant speed ghost, and rarely crash.
I would want the option of random lane changing also (with anti-collision enabled). It would be even better if the car changed lanes based on other traffic. I don't like knowing for sure what the Ghost is going to do.
Being able to save and edit these lap recordings would be a great assist in getting a good lap for playback.