"Mechs" are generally considered as that.. extensions of human capabilities, though it basically is used just to refer to any immense weapons
platform that has human qualities. (Legs/Tracks/Torso that moves independant, and Arms)
IF they ever became plausible to build the up side to them would be the massive amount of weapons they could carry. On something that large even our
current em rail (sci-fi people read... Guass rifles) technology could be fitted.
Normal weight for Sci-Fi mechs are between 50-200 tons.
This is a MOVING object. Its top speed is under 5mph but it weighs in at over 13,500 TONS.
www.wcsscience.com...
While a walking mech weighing 100 tons may be hard to fathom (only because we can't build a reliable walking anything) A track based mech is
possible. It would be slow but its armaments could be massive, Its armor could also be 10 times as thick as any current armor.
Once walking is figured out it could be a large mobility upgrade but it would have the inherint downside of overly exposed joints. I would bet on
cover plating acting somewhat as old knights armor in which it overlaps when the join moves. In that case the weakest point would be when a joint was
straight and the strongest when it was flexed.