Athough it is not mentioned in the books, i really like Peter Jacksons Concept of 'wargoats'. These would be found in the northern areas of Middle earth (Iron Hills and above) and will be a New mount added to the game.
They should Have a charge attack (like that of the rhino) and have good health and speed. They should be Around the size of 1.5-2 blocks and Hired from a dwaven Commander for 80 coins.
I had a concept of being able to create armor for these Guys that look similar to the boar armor although more expensive. This could be the crafting recipe:
L S L L=Leather S=Saddle
D D D D=Dwarven steel
D B D B=Dwarven banner(0f your choice)
Having different banner could change the colour scheme (like a blue-ish Colour For Blue mountains and red for orocarni). And the idea of the saddle being that only people with +dwarven alinment can ride them :D
Hope you like my idea and please Kudo :) -Oggy PS. here is link to video of wargoats in BOTFA https://www.youtube.com/watch?v=zZxf3hQAFb0