OK, I suppose you might get slight economics-of-scale structural advantages by hanging them on the wing.
You are aware that the wing is lifting the fuselage, not the other way round?
This is the old "you can lift yourself by pulling your hair upwards"-gag in a new form. The weight the wing has to carry is the total weight of the aircraft, no matter where the engines are and it has to be structurally accounted for. Or are you telling me that if you put fuel in the wings, or engines, that weight doesn't count?
The only reason fuel is carried in the wings, is because it's a good place to hide it. A 1000lbs of fuel in the wing is a 1000lbs of weight, no matter where you put it.