It think mechs are impractical. Sure, they seem to be a vicious killing device in Mechwarrior, but that's only a game. You have to considers the
factors in reality.
First of all it's much too big of a target. A well aimed missle can knock it off balance. Even with all it's heavy armor, there's a certain limit
to how much it can take. With everyone desperately shooting at it, it won't be long until it's on the ground, making for a very easy target.
The only good practical use I can find for it is that you can use it to stomp and blow apart small towns to debris. Even with guns shooting at it, it
can probably take a few hits with all the tons of armor. People will be running frantically away as it decimates every building in it's sight. But
then, what happens if it touches a telephone wire? The electricity travelling through the heavily metal armored machine will probably short circuit
everything, and it loses it's balance and falls to the ground and dies.
It mech is probably going to carry ALOT of ammo and explosives, so a hit in the wrong place can probably blow the thing up. The heat produced just by
firing the machine gun will over heat the systems and cause it to shut down or shot out. If heat sinks are going to be used, there's gonna have to be
a whole heck of them.
Firing a missile will also be a problem. It creates recoil, pushing the mach back and possibly tipping it over. For it to properly aim and launch it,
the mech would have to stand still, and go into a fighting stance to keep balance and launch. When you have all these people shooting at you, staying
still is not an option.
How the hell are you gonna power the thing? Moving something like 20-40 tons, it's gonna take alot of horsepower to get the whole thing going. Even
if you some sort of power source, what's gonna fuel it? You need something that can take away heat, be dense so that it can last longer, and you need
ALOT of it to have the mech running for the entire battle. It doesn't have to momentum that tanks have, so you can't coast down hills. Rolling down
is an option, just be sure to hit the enemies on the way.
Given the idea of a walking machine, I don't think it's possible to have one that can walk and do battle at the same time. Even now, we've barely
managed to make a walking robot, and it moves really slowly and had a really complex system to keep it balance.