You know, I was thinking, since we have elected to utilize tent structures for the castle systems--why not then do a system like the Dwarfs?
So picture this: We have the tent system for Harad, but their outposts would be Umbar. If we select Rhun then the outpost would be a Khand outpost. And if one were to choose Far Harad the outpost would be half-troll tribes.
This may seem like a crazy idea, but Far Harad's main units should consist of Morwaith people. Think Zulu like with cavalry being Oliphants, Camels, and or Zebras.
You could keep the power tree as is, the only thing that would need to be expanded is the Morwaith units and half-troll tribes.
I think this would be more promising and would function possibly better. I also thought of how the Black Numenorian ability to make numenorian structures could work.
Say the Evil Men are playing against a 8 man faction and Rhun is selected. The Black Numenorian comes and makes the Rhun Chieftain to the Dragon King. If Rhun conquers any other castle base, or if they have the money to purchase a castle base--then the structure becomes like the fortress in your pictures.
I don't know though, since the function would be similar to the Dwarfs--could the structures be changed based on the differing cultures? That is something that needs to be considered.
Oh for a better understanding of Rhun, Harad, and Far Harad troop types--I went to these following links for ideas and they seem to be perfect if we tweaked them to the Edain Mod.
Far Harad:
https://lotrminecraftmod.fandom.com/wiki/Half-trolls_(Faction)
https://lotrminecraftmod.fandom.com/wiki/Morwaith_(Faction)
https://lotrminecraftmod.fandom.com/wiki/Taurethrim_(Faction)
Harad:
As we currently have it with Umbar playing a big part and using Mumaks.
Rhun:
As we have it. Khand would be more fitting as their outpost since they--like Rhun, participated with the Wains.