If I had modding powers I would probably add a lot more lesser monsters (still not part of the "regular" cannon fodder though) ... and perhaps a few asian factions.
I would probably also add a Nature Based religion which worships the great bear demon of the earth .. whose specialties are wood-dryads and bear-riders/bear-knights.
Another religion will be a psuedo-immortal religion of hallow librabrians and archivists ... collectors of life and death. They would worship the angel of death Thanatos, and collect souls for study. Could probably trap souls of enemies with special swords, and perhaps extract a measure of essense or mana from them. In addition, to have certain "humans" able to train and magically altered to become powerful grim reaper units.
Also to have shadowy assasins that can move through the battlefield almost undetected until they cause havoc with their "deaths touch" ability. A much more refined, regal, and angelic form of the Death-type religion.