You though it all by yourselfs before I could give any idea... geez I'm getting too old for this xD joking. An army of it would be like if there is 100 army food, 50 would be of 1 food riflemen with deadly attack but rather slow (Something like the sniper rifles from Call of Duty: they're deadly but slow to shoot... which means they're good to take down few enemies or if there is a wave of rifles to just shoot them before they get close.) and another 50 food would be tanks and mecha suits armored, etc. 10 tanking units costing 5 food each... they would be the best that Steampunk could do. Maybe a special unit, or if you choose that technological god that I forgot the name, you already have some upgrades of steampunk. Or even a greater unit, something like that. I've saw a movie once, a anime. Steam boy, something like that... of course that compared to the steampunk thing it is quite old, but could give you guys some ideas about, since it is a pretty revolutionary use of steam for that time. And the movie is pretty good too.
Edit: Impero Machina seems good, though if they are that modern they aren't a empire... they are a force, a country, a wave... empires are old, and I couldn't think on another name, so yeah, it should keep like that. Good idea, you spawn some clockwerk men with that building... though if they do not cost any food or resources, they should be rather weak. I think there is something like that in the movie I mentioned. And you could use Necropolis model to do so, since as far as I remember the steam fortress just look like one. And if anyone here know Ragnarok, using some buildings and ideas from Einbroch would be kinda good. Like a gunslinger hero o/ which could also be the leader (not emperor, emperor is too old) of that revolutionary force, with awesomely powerful (not as the rifles) and fast pistols! And/Or a engineer that made the better mech suit in history, and lives in it. And also fight for his brethren... his machine is so a revolutionary one that it can spawn clockwerk men (too) AND it have a bathroom o/ (have you ever saw a suit with a bathroom? EVER?)