I don't like this argument at all. The theoretical warp drive is supposed to create a bubble around a ship, bending the fabric of the universe around it. How could something that exists in the universe interact with something bent outside the universe? This makes no sense to me. This thing should be able to fly through a planet without interacting with it the way it's phrased.
One of the fun things about an Alcubierre drive is that anything inside the bubble is causally separated from the bubble as well as anything outside. The bubble actually is your "deflector" - nothing outside can have an effect on your ship until the bubble is broken.
Another fun thing is that, because the inside is causally separated from the bubble, it has to be created and broken from the outside. It's more like a warp gate than a warp drive, there needs to be hardware in place at your destination to stop or they won't have to worry about the blast of particles coming out when the bubble breaks, the bubble will just smash into and through the planet. The ship will of course be fine nothing outside or hitting the bubble can have an effect inside, but the planet... well, I'd like to see theories on exactly what will happen then.
So, the particles get released and punch everything to oblivion..
The ship has to stop when it reaches the destination.. true. But, it doesn't need to stop all of a sudden. If the particles could sweep in the bubble (as the theory says) and get released when it stops, then they are also moving at super-iluminal speeds. So.. maybe a solution could be to try and decrease the speed gradually once the destination is getting close, so that everything inside the bubble (including the particles), can decrease it's speed too. Allowing for a safe stop.
This seems so easy that I'm probably only saying garbage