[Rupert]

That sort of thing works against something in a fairly low orbit, but GSO is about 35,000km up. Thus launching something in Earth's shadow only gives it a limited time before it comes over the horizon, long before it reaches GSO altitude, and it won't be following a very different trajectory from that of the ICBMs anyway.

Also, everything you launch in the kinetic kill cloud is mass not devoted to nukes - the launch platform is going to be the same in both cases if you want to lift much mass, because the long range high-throw weight ICBMs are really the only platform we have in any number with the reach, and there aren't many of them left these days either.