[Suggestion] Multiple Engine Sounds
There's nothing more disappointing than building a military rover or a race car and hearing the dull whir of an electric engine, or the same hydrogen engine. So: give us four or so new engine sounds. Players could emit them from the sound block already in game, or you could introduce an "engine" block that plays the chosen engine sound in place of the default sound.
The key of course, the engine isn't simply a repeating sound, but modulates it's sound according to what the player is doing (heavy strain on the power draw, light strain, etc)
-Heavy construction engine
-Light Rover engine
You could also make it DLC.