Sound Customization.
Add the ability to all "bricks" that create sound (That being engines, acuators, guns, etc.)
to change their speed, pitch, tremble, bass, volume and such. This would greatly improve how unique each vehicle sounds and would let the players make them more realistic, also multiple sound presets for each would be nice. For example acuators having the "scraping" sound they currently have but also electric motor as an option.