Does anyone use gravitational slingshot maneuvers to navigate the star systems faster? I kinda think it should be a thing. I know there are hyperspace storms you can use to speed up your travel through hyperspace, but not really the same thing.
Gravitational slingshot requires relative speed to the targeting celestial body. Also, it can work one way or another: it slows you down if you enter the gravity well in certain directions. To simplify the equation, you gain approximately double the velocity of the celestial body's.
It's not that it'll be difficult to implement but it's rather that being impossible to implement it in a visually intuitive way.
Also, the celestial bodies' speed ain't that impressive comparing to scale of things in this game, to a degree that it's safe to be ignored.