Board Thread:Suggestions forum/@comment-28813058-20160730193323/@comment-26172435-20160731080343

If any mount for Dunlendings, I'd opt for donkey-sized ponies. Note that Dunland is a rugged land where shorter legged sturdy ponies will have an advantage over the long legged, elegant stallions of the plains.

As far as I understand the mod team doesn't wish to add all 'possible or even plausible' units for each faction in order to maintain a certain level of uniqueness for each faction. Same reasoning holds for DG berserkers and dwarven archers.