I have some ideas to share for this faction. I have written some of them on Moddb. My opinion about this 'Easterlings and Southrons' named faction is maybe not entirely but categoricly summer form of Angmar. General system is Rhun starts; wind mill, variag tent of Khand, corsair tavern of Umbar are settlements and Haradrim Camp is outpost. The relationship with Angmar is hero-center that meaning of the Witch King is Khamul for Rhun. We know Rhun was an alliance to Mordor at Khamul's time. However there is influence of Sauron and WK, not equally but similarly must be in this faction.
Buildings of Rhun can be wine-market(can be used for Dorwion also) ,seafood-market, armory(banner carrier,forged blades, shield for infantry and cavalry, fire arrows), barrack(rhun soldiers, archers, spearmen), stable(rhun riders, wainriders(selectable for wagon or chariot)), temple of Melkor(sorcerers and illusioners which use fire/flame and shadow), tower, statue of sauron.
On the settlements variang tent recruits axe-men infantry and cavalry. Orginally BFME 2 used corsairs for light infantry like Dunland clan for Isengard, i am intent to do it that way. So tavern should be on settlement and recruit corsair plunderers and archers, plus ballista, maybe assassins max 3 time.
Haradrim Camp is very questionable to be seperated faction. Being solo faction to Harad makes Rhun so weak. Also Harad do not have direct relationship to Sauron over a ringwraith. Rhun is more defensive but like half-cavalry faction, it cames from far lands. They do not have siege machines their own, to do that they need a settlement or an outpost. Agression of Harad is really force for Rhun. Their fortress can be like RJ Rotwk mod's: in the front statue of dragons can fires or snakes, buildings are farm, haradrim palace(haradrim warriors, archers, spearmen can switch throwing and black serpents max 3), mumakil pen(mumakils and half-trolls).
Rhun economy is based on trade so we need to use this. Building level up system is like dwarves when markets and wind mill get level 3, others would levels up except Temple. Temple can one level up after Fankil's created, then maybe Fankil gets level 5 because it is connected directly to Melkor through Fankil, not to economy.
Heroes would be Khamul the Black Easterling(building supporter?), Fankil(mage or unit support), Suladan(mass slayer), Saleme(hero killer), Brodda or Lorgan King of Rhun, Sakerlan King of Khand(could be building destroyer), Castamyr Lord of Umbar PJ
Ring hero system is very different. These men do not have an ethical rule nor discipline. Their reputation is not trusted or reliable. Everyone betrays the others when has the chance to be rich or get the power. So each hero must be ring hero but ones they picked up the ring they shall not have for second time. The influence of ring is different for every hero, Khamul and Fankil shine through but when the others get the ring can be rich or being a commander of large armies. Fankil can turn into a new Sauron and Khamul can make every allied building %25 faster.
For spellbook i will not say so much before approvement of these. Somehow it can be done, there are scorpions, snakes, sank storm, etc to use.
I hope it is not over powered. Heroes and their rolls or units can change actually everything can change. I just wonder what is your comment.