It turns out the splines in 4.3 are amazing! We were able to drop a SplineComponent into our level to represent the track center line, which we’re now using to tell the shared camera which way to look (with smooth movement) as vehicles progress around the track. We’ll also be using multiple splines for the AI.
Also I’m planning on posting a video soon running through the vehicle physics in more detail - we’re not using the inbuilt UE vehicles, we wrote our own custom solution so we can mess with it in cheap and nasty ways to do our bidding.