You're spot on with the Millennium Falcon comparison. One of my inspirations was the 12th level of Super Return of the Jedi from the SNES, where you play the turret gun during the Battle of Endor.
As for the audio, you should only be hearing two sound effects: the sound of your ship's engine running, and your gun firing (I made both sounds during GGJ19, and reused them here). Trying to add more sounds, like other guns firing, became too much of an auditory mess due to the sheer number of Audio Sorces. I didn't get to music so there isn't any this time around.
Blocking it out with Unity shapes actually ended up being a major boon, as it gave me a lot of control over the prefab, which became important with locking the turret rotation so that ships can't shoot themselves while tracking opponents.
My biggest disappointment was that I couldn't get more ships into the scene. With syntax being my Achilles heel, my code was definitely not optimal. Too many ships and the game crashes from how many vectors it's trying to calculate at once.
