25% of what? Because I can guarantee it wasn't airframe weight, or even fuselage weight...
It was 25% of the weight of the structural elements of the fuselage. The structural sections could be optimally spaced, and smaller not having to reinforce around the windows. There is the weight of the window assembly, and associated flashing to consider.
The window assembly, associated reinforcement, and extra strength for each member, vs a thin layer of aluminum?
How can you guarantee it is not 25%? Did you read the Airbus information?
How are you going to do that without windows?
As shown by the Airbus patent and the article. There would be screens instead of windows, and cameras mounted on the outside of the aircraft would provide the same view.
Airbus also patented the pilot in the cargo holds, aviating by screens and cameras. Likely a much better view than the current windscreens, an probaly much more roomier flightdeck.
One uses screens in the sim, so what is the big deal?