Maybe the mod designers could add something similar to the MOS call for Dale's aid when Erebor is attacked. It's a Silvan Elf version, except that the Elves simply say 'No' before walking away.
(Seriously, it's like Thranduil only cared about the dwarves because they had money! What a shocker.)
In all seriousness, Elk riders are a big no-no. I don't have a problem with Thranduil riding one, but not in the game! Definitely adding Dale units is a good idea, although all the Dale soldiers I saw, were on the screen for about a second before disappearing in a blaze of fire.
You could probably let Azog be a special unit, his special ability being, Egg-Whisk, in tribute to his prosthetic limb. Or maybe give him a set of prosthetic limbs. A Swiss Army prosthetic limb! Capable of opening bottles of wine at social gatherings, to impaling a dwarf in the face!
Makrell...NEVER mention anything that could possibly relate to that fraud of a wizard Radagast in my presence! I will not suffer him in the game!