Oh, I know its totally impossible (by modern standards), I just think it looks shibby, and the idea of huge mecha pwnsaucing turns me on.
Technobabble is as follows
As to the armoring, I use Nachtium as you may remember. It only can be created in a crystal lattice, and because of it's massive density you only use it in very thin layers, but is a massively strong building material (think of building a skyscraper out of steel vs out of wood). This means the mech is not only highly armored, but also can support its own weight. This means it's also immensely heavy, which can be solved easily by counteracting repulsor lifts.
Honestly these creations aren't meant to win battles by themselves anyway, they're just supposed to be awe-inspiring and pretty frikkin cool.
This is future-tech people, nothing is impossible, and if it isn't cost effective, who cares? None of us actually need to participate in real ground combat anyway, we're perfectly capable of just blowing up any dissident planets, and moving right along.
