For the mech I want to build, I just want to walk to work in it. As a conversation piece, you know? That and I have a fascination with ballistics, and caseless ammo. Good for shooting off some rounds in the arizona desert. A tank would work a LOT better, but the mech has the 'coolness' factor.
So no pressure responsive suit for movement, that leaves control sticks and foot pedals. You'll need a seperate controller that can synchronize all the movement so you don't have to manually move each leg and arm. If you swing the arms, that can help shift weight around so while you have a leg up you don't tip over. What about a fluid ballast that can be pumped around to move weight? Think mercury would work? But the EPA would love to a giant walking mech that pumps 100 gallons of mercury around to just to be stable. I'm not too familiar on how gyro's work, but I think you can get some small ones from model rocketry suppliers, but I don't know how to interpret the output.
Currently the US Army is working on an exoskeleton, but they're using nanotechnology and its soldier size. A monster sized one would be a lot neater though.
As far as power, I was thinking of a fuel cell that ran either off methane or hydrogen. A water splitter would be neat, but I don't think those work. The trick is getting a hold of a fuel cell with enough to juice to power all those heavy duty motors, then watch your fuel! You'll probably need an emergency 'let me out of here' door.