I think he's just saying it would behave like a chariot, being a gigantic trampling unit. But it would be different from the Gath chariot in that it has 100hp, as he said. Also, I'd imagine it's this hulking metal monstrosity that is far better armored than any other chariot, in fact it's sort of a Blacksteel War Chariot, which could be actually powered by 2 mammoths completely ensconced in the steel body of the Machine.
The Terra Cotta soldiers sound a little excessively powerful, especially as sacreds. But that sort of thing is great. I just really think that the system of forcing it to be managed as a summons is the way to go with it. Even at 1200g and 200 resources, you would want to buy that ASAP. Why? Because you could take 3 indy (or low-mid PD) provinces at a time without a single loss, and if your neighbor had 45 sacreds with 20 prot and 45hp, and you didn't? They would slaughter you to the last man with no question of victory.