Premise
So yes I have read the FAQ and I know that no more factions can be added, but I also know that we can do subfactions in the form of what's available for Erebor or what is being done with Adventure Factions for 8.0. I am relatively new to AotR, but I played BFME back when it first came out and I have recently come back from a very long hiatus. I have always dreamed of having a Rhun faction, to me they always were by far the most interesting of the people groups that Tolkien gave vague and mysterious hints and insinuations about in the lore. Needless to say I was quite surprised when I discovered that the great mod AotR doesn't even include them as a subfaction, So I would like to argue in favor for its inclusion as a subfaction in some form. Here is my reasoning...
Arguments
"We decided against Rhûn early in development of Age of the Ring due to it requiring a far greater degree of fan invention and wasn't as interesting as a potential setting as the vast deserts, jungles, and creatures of Haradwaith."
-This statement leaves me rather confused. Far greater degree of fan invention than Harad? Really? I mean no offense, but every single one of the heroes in Harad is a fan invention and the units of Rhun would be inventions to the same degree as those of Harad. In fact, Tolkien describes their armament in passing just as well as Harad's and we have flat out gorgeous depictions of Easterlings from the films. We don't have names of tribes and clans in Rhun, sure, but there are a few vague regional names available for enough to work with in my opinion.
-Also, Rhun offers a vast amount of settings as well. The Sea of Rhun itself with its rivers and islands, the steppes or plains to the north and east, the forest of Neldoreth northeast of the Sea of Rhun, the Orocarni Mountains and its four dwarven clans, the expanses of Khand, the East Sea, the mysteries of the Wild Woods of Hildorien which as far as I know were never destroyed, and the Last Desert with its were-worms (who cares if it's just a Hobbit myth, it has just as much lore backing as the apes of the deep South).
-While maybe not as abundant in strange creatures as AotR's Harad, we actually have to work with less fan invention than giant vultures, scorpions, or hyena wargs. Namely there are the earlier mentioned were-worms (whatever they are), along with the Kine of Araw (giant auroch like creatures) and the pards (giant felines of Hobbit myth), all of which are mentioned just as much as other mysterious creatures in other factions.
I've also seen arguments suggesting that Easterling units should remain in Mordor because of their close connection with Sauron throughout their thousands of years of servitude. They were an essential part of his armies in the Third Age.
-Honestly I see this as more of a reason for their separation, for same could be said of the Haradhrim and Umbar, who sided with Sauron almost since the beginning of their history, or factions like Dol Guldur which were literally led by Sauron himself at points. Rhun was part of Sauron's plan since the Second Age, in fact he was accredited with uniting them then and bringing them into civilization. After his fall, both in the Second Age and in Dol Guldur, he fled to the East where he had great support. To me, this shows them not as part of Mordor, but part of Sauron's greater design much like Dol Guldur or Umbar. If anything, Rhun was the center of Sauron's identity as the "High Priest of Morgoth", not Harad as AotR seems to be leaning towards.
-Along with this, Rhun displayed the same amount of autonomy from Sauron that Harad did. They had their own leaders, though not named, who led them in multiple invasions of Gondor and Rhovanion (more than Harad did btw) throughout the Third Age, over which Sauron had no direct influence. There also appears to be some strife within Rhun itself, with Tolkien stating that the Blue Wizards had managed to diminish the forces coming from Rhun by helping stir up rebellion. This shows that they were not just another mindless horde of Sauron.
-The removal of Easterling units from Mordor creates a hole I realize, but I think this could be filled with two possible solutions. One being adding more Orcish units which I could give some suggestions for. Secondly, making it so each of the different "Evil Men" auxiliaries are available as opposed to just Easterlings, this could be done in several viable ways.
Conclusion
So that all being said, I do have actual suggestions for what the roster and heroes could be like that I would be happy to share if there is interest (Clans, dwarves, Variags, war wagons, legions, and beasts, oh my!). I recall hearing that part of the reason you all decided to do an Arthedain Adventure Faction was because someone gave suggestions that made it seem interesting, so hopefully I can do the same! To be clear, this is not a suggestion for a new faction, but I subfaction. I think the best option would be to give the player a choice of Rhun or Harad (as I believe Harad's mechanics fit well with my suggestion), as Adventure Factions are too limiting in my humble opinion.
Please correct me if I'm wrong anywhere or have said anything forbidden. I have really enjoyed this mod and appreciate the hard work that has gone into it. it's because I enjoyed this mod immensely but personally feel that to be complete it should have Rhun. I'd be willing to help make it happen. In the end, this mod belongs to the AotR team and they decide what makes it complete. I only want to throw out my thoughts in the hopes that it creates inspiration and maybe can make Rhun look interesting enough to change their minds. (edited for clarity)