while the idea is cool, they'd be too slow in real life.
it would take all of 3 seconds for a human to target this thing and blow it off the face of the map. while it probalby takes it atleast 10 seconds to move, turn, aim and fire...and thats only for stationary targets.
the only way these would work is if we were literally invading some country. we'd need thousands of them to form a line, then have them blow away anything in its path. otheriwse this is nothing more than a robotic bomb disposal unit with some rockets and guns, completely pointless IMHO.