Thanks. Yes Pitch shifting is easiest and I'm actually using only one loop rather than crossfading (although that is how I would normally go about it). Recording the engine-under-load loops is a bit of a pain if you want to do the full deal as you need to have the car seamlessly looping at top rev for 5-10 seconds without moving too fast to introduce too much wind noise. When I did my recordings I had to keep it in first gear, apply brakes, find a quiet road that sloped upwards and I tried to keep the rev steady at 6000+ RPM. That's the beauty with the acceleration ramp recordings - they are much easier to obtain and I think the size is smaller which is a bonus. But regardless, with it being an arcade-like looking game I would probably lean towards using the single loop (as in the video showing the time scale) to match the low-poly look of the game.
Yes, the game speed is tricky. I will simply have to play test and gather feedback and determine to go for sim-speed, fast-speed, or cater for both groups of players. I hate choices yet I always end up having to make them somehow :)
I plan to add support to extend with as many vehicles as possible. I will make them as downloadable asset bundles so a car will come with its unique model, sound effects, handling, and part upgrades. I plan to allow the upgrade of the car so people that prefer grip over drift can simply invest in grip-increasing upgrades whereas those that prefer styling or performance upgrades can choose that. I think I will base match making based on how upgraded a car is so if you have a low end car with a massive turbo you will get matched with cars that have a much higher spec originally. I think that way it would look more fun too with different car models and everyone can race their favorites.
Thanks for your feedback, it's very valuable to me!