Doesn't work like that. Load factor is effectively a force proportional to the weight. Just because the wings don't fall off doesn't mean you can exceed 2.5G on the rest of the structure (think cargo hold flooring etc).
Not sure what you're trying to prove re GPWS performance but you're completely wrong. Nominally the light and heavy aircraft will achieve the same acceleration in the pitch axis but the flight path change in the lighter aircraft will be faster.