Spitting Droid = Missile Deterrent
The MKV would have to hover in space, continually reorient itself as it locked onto new targets, and spit out vast numbers of projectiles.
The video shows they've got the hovering part down, at least.
The video, though genuine, looks weirdly like pretty good CGI.
Ares notes that the device bears a weird resemblance to the hovering droid that that spat out bolts at Luke Skywalker during his lightsaber training.