I stand corrected then, an active propulsion system would work better.There was a post here, apparently winged kit not suitable for bunker buster as they need to hit fast and gliding decrease the speed.
How about making it detach after a certain point then? Launch it with the wings, at a distance that it can drop by itself to the target, wings detach and let gravity do its thing? Targeting solutions like GPS maybe could be used to program the kit.