In the case of the Harrier, and thinking out loud, but what about jury rigging a pair of those self contained ex-F4 Gatling centreline pods....one each under a wing pylon.
I guess the wing pylon and wing attachment would have to be carefully watched/ inspected to look for stress fractures. There must be a hell of a need to disapate cyclic loads. What about the electrical & electronic control systems required to enable that fubctionality.
Your probably right, spec we can just tape the wires along the wing edge.