[@Willy Vereb]If I were you I'd make Ogre a different species, but still allied with your army. I was planning on using Ogres to be apart of my history as they are classically depicted to be something Dwarfs sometimes fight, which is why most of my units would be (semi)anti-large units. Then again, Trolls were going to be the bigger threat.  

You could make the Olog-hai like in LOTR.