Why not instead of 6 asteroids, we place 1 gas giant each, and you have to maintain a fair distance from them or else incur a red stress token? Then the ships would have to accelerate away and once free of the gravitational pull, perform a white move? That would be a real test of piloting skill. You could use the gas Giants as ways to lure your adversary in for what seems an easy kill, but leads to a possible loss of speed and movement?
Scale. Gas Giants are several times the size of the Death Star.
But scale doesn't matter; if people say we can have a Star Destroyer Ingame, why not gas giants!
*runs away in shame before the other community members kill him*