That sounds great! I've always felt that goats would be better mounts for Dwarves than the boars they use right now. Additionally, the mod's boars seem comically small for their riders. (Though I think a slight enlargement may be in order for the goats as well)
And what about goat armor? Should it be Dwarf-Exclusive like the current boars, or craftable using vanilla materials?
- 1: Give Ered-Luin and Erebor Dwarves goats, and give the Iron-Hills Sub-Faction Boars. This would make the Dwarven Factions a bit more unique in my opinion.
- 2: Replace Boar Riders with goats, but give Dwarf Commands the chance to spawn riding a Boar.
Of course, having them mixed (like the Haradrim with camels and horses) is also a possibility, but I think its unnecassary to have multiple-mounted units for one faction (unless they're divided between Sub-Factions).
I have an idea regarding the way they should spawn. Every military force has its scouts, and the Dwarves should be no exception, as they would most likely be extremely vigilant after just reclaiming Erebor. To model this, Dwarven riders could spawn around the borders of Dwarven territories, perhaps even in the wilderlands from time to time.