I really want to join another Avatar RP, but I'm hesitant for the plot to be "one nation is taking over everything."  Because that's been the plot twice in the actual shows, and is extremely common in RPs.  

I would also say that a [i]human[/i] seeking to encase the world in ice is a bit odd.  I can't get my head around her motivation for that.  

Both issues would be very well put to bed, of course, if we bring spiritual involvement into this.  Maybe Iluq has been fed madness by some ice spirit seeking to expand its realm.  Heck, maybe she's even been full on replaced by it.  The spirit is lending her power, rather than her having recruited Water Tribespeople to help with the insanity.