Originally Posted by
lucille
On the other hand, wings which don’t need to carry fuel can be made a whole lot lighter
I think the opposite is true.
if the all load is carried inside the wing, then bending stresses are reduced. If the load is carried in the fuselage, then the wing bending stresses are increased. Maximum zero fuel weight is due to wing bending loads. Fuel can then be carried in the wings up to max take off weight.
If all the fuel is carried in the fuselage, then the aircraft wing structure must be beefed up (extra weight) so the zero fuel weight can be increased up to max take off weight.