Lost interest in LFS for good/for a while/until something big comes along but here's my 0.12 Finnish markkas (2 cents).
Recording engine revs:
VERY expensive to do properly. You'd need many mics - both dynamic and small diaphragm condensers placed at various distances (dynamic up close, possibly stereo mic set in driver's head position and possibly LDC or two for ambience). Impossible to on a highway as road and wind noise would come through. Even on a dyno you'd possibly encounter unwanted reflections from the walls.
Does LFS have enviromental audio effects? It does have cockpit muffling (?) slider in the engine sound editor but as far as I remember it acts like a soft low-pass filter. Could a VST-based impulse reverb used? That way you could create impulses from real-life car interiors (race cars vs. road cars... open wheelers do not apply!
) to make very immersive in-car audio enviroment.
What LFS really needs is lots more ambience, chassis and suspension clanks, tyre well rattle from small rocks, seatbelt suffle and various creeks and dings that should make you feel like the car is about the crumble to pieces when you plow through the chicane curbs before your wheels fall off eventually.