Timerover51
SOC-14 5K
Even adding more asteroid sized bodies into close orbits of the gas giant should be possible. Lots of rocks racing around it will complicate navigation and maneuver in and out of the gas giant. I doubt getting hit by 10,000 tons of rock at thousands of KM a minute would be good for any ship.
Have you consider exactly how many rocks would be needed to pose a danger to ships using skimming, and what the energy requirements would be of moving them there and placing them in close orbit?
Two additional questions.
How long does a System Defense Boat stay in a gas giant's atmosphere before it has to return to its base, wherever that may be?
How many System Defense Boats would be required to cover either Jupiter or Saturn?