What you're doing, when you design the wing/pod(nacelle) interface is trying to minimize the penalty of having some ugly lump stuck on the wing, screwing up the wing aerodynamics. I'll stick my neck out a bit and say that no external shape added to a wing other than for purely aerodynamic design reasons will improve the wing aerodynamics, compared to that you'd get if the aerodynamic design were not constrained by the need to have a pod or nacelle with something in it.
I would go on to say that as long as it is sucking and blowing the nacelle of an engine does not have significant drag and an attempt to construct some sort of airfoil under it would probably fail as a result of engine in operation. Do not forget that you do not create lift without creating drag. That motor only becomes a significant source of drag when it fails in flight.