Who said the X-37 has to survive though? That can do a 180 and decelerate using the main AR2-3 at the cost of a decaying orbit then drop the payload at 4km/s.
Of course the vehicle is going to be destroyed anyway, so just carry the payload all the way down till it goes boom or whatever, unless you were hoping to launch multiple warheads. The problem is the whole vehicle is very light, so you're not going to fit a B-52 worth of payloads in a vehicle who's launch weight is, I believe, lighter than a GBU-43. My point being that if vehicle plus payload at launch is lighter than a GBU-43, there's not much point in being concerned with how many GBU-43 it can be dropped if it can only carry a fraction of one anyway.
The main problem is its hard to think up a mission profile where a cruise missile wouldn't be cheaper and more effective.