... With directional antennas, it is much harder to jam them in the air, as you can filter out any signals at a little above the drone's altitude and below. So, you'd have to be ABOVE the drone to jam GPS signals. This limits the available platforms to electronic warfare aircraft, but with a movable directional antenna, even these signals could be filtered out without much difficulty....
Wow. You have decided that electronic warfare doesn't really work at all, since an incredibly weak signal (10^-16 watts per square meter) can be detected against a 200 watt jammer directly overhead "without much difficulty". Electronic warfare experts everywhere will be amazed. The U.S. Navy only has the best electronic warfare planes in the world.
First off GPS antennas detect signals from satellites in different parts of the sky - they are non-directional (or else have a very small gain since they don't need to look down). Second, the jamming signal strength will be on the order of 100 billion times stronger than the GPS signal. Only a gain of 110 db will overcome this jamming signal, and the highest gain antenna in the world in the 305m Arecibo radiotelescope with a gain of only 70 db.
This also means that the supposed telecomm link to the army of controllers via satellite (must be geosynch to stay in position for hours) cannot be maintained. A high gain antenna would work here, but a 60 cm satellite dish only has a gain of about 35 db, meaning the jamming signal will be 10 to 100 million times stronger.
10,000 drones churn around completely unguided whenever they come within miles of the ships, while any that blunder into an intercept trajectory get blasted with 100% success rate. Number of drones hitting ships: zero.