Sounds like a good way to hide a first strike. As it passed over enemy territory you could just say there were errors in the design and cause enough confusion until it was too late. Of course you could only launch one weapon at once (but it could be a MIRV), but since it would be a surprise it might be possible to knock out the leadership of a country, because they wouldn't go into hiding like they would if they really thought a nuclear war was going on. "Oh that nuclear submarine near your country launching an ICBM is really launching a satellite."