You make a good argument, but I have to point out again that we've been inside of the Crystal Tower, seat of power in the Allagan Empire, and saw nothing resembling what we would consider a flag. That leads me to believe that the Allagans simply didn't have one. Heraldry, possibly. Probably, even. But something they could point to and say "That is the visual representation of all Allag and it's peoples", I have to doubt it. And maybe that's just a cultural thing. I mean, there's no natural law saying that the concept of "unity" is represented by a flag. Somebody just made that decision at some point and it stuck.
