I live with a highway just outside the property lines of my house, and everyday I hear semi trucks engine braking as they pass by my house. At first I thought it was the sound of cars hitting the rumble thing on the side of the road, but I learned it is semi's engine braking. So I would love to see this in BeamNG.Drive. Here is a video example of what I mean. Skip to 0:28 for the engine braking I would describe the sound as sounding kind of like race cars running over the apex on the side of the race track.
I got even another idea! Brake squeal sound for RACE BRAKES. I remember a little while ago I rode in a heavily tuned Nissan GTR, and it had race brakes. And whenever the brakes were pressed, the brakes would squeal very loudly. I find this sound very satisfying and would love to see it in BeamNG!
Yes, the Jake Brake is a very satisfying sound. Should be doable by changing the brake sound file with a jake brake sound file.