It might be more fruitful to make Mars the moon of Venus, put that combination at a trojan point to earth, and bombard earth's moon with comets. The would leave Mercury with no use.
Or make Mercury the moon of Venus and make Mars into earth's moon and send the moon into free orbit in the asteroid belt and bombard it with all the asteroids and comets until it is big enough to support a mining colony.
That seems like an awful lot of work. Why not just ignite Jupiter into another sun so that we can colonize all of its moons? Except Europa of course.