Thanks so much for the detailed reply!
I am so glad you brought up the granular synthesizer, because having watched your recent presentation, I did wonder if I could try using it to essentially timestretch the vehicle engine audio and then scrub through it. 
I am definitely up for experimentation and will give this a try. I suppose my only other question on this point would be when would you expect the new audio engine to be officially ‘switched on’ rather than just available by editing the .ini file?