[quote=ASTA]
...if it's made out of lightweight material, why is weight an issue?The bolded point sort of contradicts your paragraph's first statement/argument.
[/quote]

you contradict your own point. your mech weighs 80 tonnes. That is nearly twice the weight of any other mech created so far. Piles of junk are unstable and assuming each of your feet are a square meter (which would be quite large), each foot is putting the weight of 7 full size H2s(to use your Hummer example) on a space smaller than a kitchen table. You would be buried in junk before you could even take a second step.