Yeah, I know the theory is that we can immediately react to a situation anywhere in the world with an unmanned system that none of the probable targets can defend against, but I still see three colossal drawbacks:
1) The "lets warn everyone in the world, except the loonies in the target country, prior to the the launch" problem. Of course the loonies won't find out, because no one in China or Russia who is supplying them with arms will bother to make a cell-phone call to their customers in advance of the strike. Nah...
2) Forgive me for asking this, but don't ICBMs cost around 60 million each to produce? Admittedly that is the cost of the Nuclear armed variety, but do we really want to pay astronomical costs to pop one (possibly empty) building or terrorist training camp?
3) The UAV/Hellfire or B-2 with JDAMs advantage is that you can actually monitor the target and then choose to engage or to recall. Once an ICBM is sent off you are committed to eithering going through with the strike or having launched what becomes a very expensive bottle rocket.
BTW - What kind of conventional payload would they have? You'd probably have one big payload rather than several MRVs if it was conventional. Either way the bucks to bang ratio isn't going to be very good.
- SEAGOON