Kiwi homebrew cruise missile
Slightly different engine choice but it may be interesting to look at the construction / electronics that were use in the home brew cruise missile put together here http://www.interestingprojects.com/cruisemissile/airframe03.shtml
use of jigs to create foam blanks for coating with GRP look like the way to go for a cheap construction method.
What about using a multi stage rocket stack to give more then 2 or 3 seconds of burn time?
The question of flight control for the landing will be interesting especially as the aerodynamics of the craft will need to be understood to have any hope of "flying" the craft back to a known location. Again the Kiwi experience of flight control electronics could be interesting specifically the expertise needed to actually develop the aeronautic software.
The other option is to not attempt a guided airframe but use passive methods such as helicoptering using stowed blades. It may be that the basic guidance controls for a helicoptering device are simpler and the idea of helicopters from space will send the tinfoil hat brigade to their bunkers!
Biting the hand that feeds IT
