Um, hi here. I have a couple (minor) ideas. Not sure how they would directly fit in though, if at all. I think what I have in mind is more suited to indirect plots that would have very little if any effect on the war itself.
As for the ideas/characters: I know you said no god-like or uber characters however, I thought it might prove of interest to you to know of some side stories I hope to do with these two characters of mine in the sandbox style that this site is known for. Meaning that they would be separate to your event. The characters in question are an Angel of Peace and a Valkyrie. They are strictly sideline characters only.
The angel's role in this is trying to find a way to somehow end the conflict as she has a vested interest in this. She does not condone violence and will seek indirectly to heal any damage and turmoil that has been caused. Keep in mind she does NOT fight nor will she have any major influence either. I was thinking something along the lines of dealing with the war's aftermath and observing the duration of the war from the sidelines. Trying to serve as a source of peace and comfort in hard times or some such. But not having any major super powers that would undo all your hard work. For her, it doesn't work quite like that, it would be a long process with others like her working together from the background. Make sense? I don't actually have her profile up (yet) but I hope to soon. Then you can read it at your leisure. One of the main things about this character is that she does not directly step foot into a war zone as that is not her style. But more on the profile to come.
The Valkyrie though is a bit different. Since you are forbidding any outside influence in the case of fighting or direct support causes, this one will not be fighting either. However, her main task is to collect the souls of any slain warriors that she deems to be worthy to take back to Valhalla to prepare for the final battle between good and evil. There was one character I think is deceased from the war and I will have to PM that person to ask about potential threads regarding this. If they are even interested that is.
Just thought I'd mention all this for food for thought. I will admit I have not read all the info pertaining to the war (as there is a LOT) but I will hopefully get to most of it. Not sure if you want all the threads/story lines read too or just the main stuff. And reread the Connlaoth page too as I need to freshen my memory of it. I also would like the angel character to perhaps take a role/side role in the Essyrni slave uprising. But other than that, I have no other details regarding that at this time. I need to read the information first before I do add in anything else.
I'd love to know your thoughts on everything I've brought up.