What material do you want to make your heavy walking sound on? (wood, metal,...)??

A good approach is to think in layers and additional sequential sounds that are connected to the walking sound. You would need top, mid and bottom layers.

Bottom can be anything heavy sounding, maybe just a high cut kick drum.

Mid and top are the more defining sounds and mostly the ground material seems to be around the harshest top frequencies (about 5k) within our hearing range because we humans needed to hear the predators moving in the grass.

Maybe the jug is ok if you saturate and compress it nicely and most likely EQ the crap out of it.

Sequential sounds like the hydraulics or servo motors are important in defining what kind of mech your player is. Also depending on our walking speed we have at least heel and toe sound and most likely release when running.

That's a lot to think about. Try not to hold on to just one sound because it will sound too much of itself and not a mech sound.

I don't know if it's possible, but you might give some thought to getting on a construction site with heavy equipment. Ideally, you would record something that weighs a few tons being dropped. Maybe if you have an uncle that works in construction or something. Not sure exactly how it would work, especially as security conscious as everyone is these days. But if you could capture those sounds it would be pretty awesome.

You might also experiment with pitch shifting some things down. I'm not sure if something that big dropping is at a lower frequency or not, but something in my brain is telling me 10 tons dropping does not sound like 10 pounds dropping.