Don't sound too excited!
Seriously though - what you are proposing is wide-scale, indiscriminate destruction, which at this point is more easily achieved with nuclear weapons. The two main problems with this are the radiation and a nuclear winter caused by dust. You would still get the latter with wide-scale use of kinetic missiles, the radiation is generally localised anyhow.
But this goes beyond a "can it be done" issue. The technology to wipe out a population exists in nuclear weapons, but this neglects the fact it should never be done. There is no effective justification for killing the population of a whole city, and in the modern age hopefully the area bombing of WW2 and the crazy days of MAD are behind us.
The future of space based weaponry would be more in the area of pinpoint attacks from an unassailable base, whether via conventional missiles or even a smaller kinetic missile. Fired down at high velocity into Tora Bora for example a small missile travelling at thousands of miles an hour would likely be as effective as a daisy cutter, and would not require shoving out of the door of a vulnerable C-130.
I would dearly hope that someone with the desire to kill the population of a city and still occupy it never comes into contact with the type of technology you propose.
