Yes, I understand relief bending moments.
The present wing has to be built to be strong enough to carry a full load of fuel when parked and also strong enough when loads are in the opposite sense - I.e. strong enough to provide the required lift when the wing is empty.
My thought was if the major load was only in one direction, I.e. lift, then lightweight composite wings could be built lighter. But, hey, I’m not a structures guy.. so always happy to be corrected.
It will be interesting to see how these 12 Dash 8s work out in the real world.