I really like the mod, I used a somewhat outdated guide so was kind of surprised when the two towers war started. I looked the change up in the logging and found it under version r3506,

This change was implemented:
"Reassign factions at begin of the War of the Two Towers, based on player standing"

What would fall under "player standing"?

I tried to get Khand and Harad to join the eye and I have fairly good probably better relations with them. I play as an uruk from Dol Guldur.

I did buff my rank by one with the quadrupple effect for rank points to make sure they are superior to other factions (Harad and Khand stand at 9) besides Mordor or Dol Guldur no other faction is at 9 some are 8 though. In my attempts it happened that only one other faction joined the side of the eye or almost all factions.

Is there a way this assigning can be influenced? What factors weigh in the strongest or is it in general a bit too random to be influenced?

It did bring to mind the idea that the possibility of having nobody joining would also be interesting as to drag out the game a bit.