Solving this problem for the tanks is pretty easy, you could purge them with inert gas (nitrogen, CO2, etc.) and then seal them to prevent air ingress or you could fill them solid with liquid (fuel, water, etc.). To prevent explosion of the tank, you just need to prevent a mixture of fuel and air from accumulating in the tank. Once fuel is in the tank, it will be very difficult to remove it all. Best to focus on eliminating the air.

 

The balance of the wing is where the difficulty lies. Any voids where flammable vapors can accumulate are potential problems. Larger openings can be protected from exterior ignition with metal flame screens.

 

If all of your conductive components are electrically connected, then you shouldn't have a problem with electrostatic discharge inside the wing. The only issue with the non conductive parts is that they electrically separate the conductive pieces.

 

Rob