I think it would be organized and best to establish a walking order, just to eliminate confusion in the thread as to who is standing where. 15 people can't be walking side by side in the Brecilian Forest, and it maybe beneficial to set formations for 2 wide, 4 wide, 6 wide. Strong fighters split between the back and the front, squishy people and ranged fighters in the middle.
This is just a default order, and a party member can break this formation. It's merely a guide to help the player know who they are ordinarily standing next to or fighting with during an ambush. Some examples of how this is useful:
Falina needs to tell Faer something, she can run to the front of the group, and know exactly where he is standing (and who with), and she knows that Dolain can't overhear, because he is far in the back.
No need to continuously restate walking order when starting a new thread (establishing threads can be exhausting, will 15 posts of Falina and Cormac are in the back, and they can't see what's happening. It's assumed that if they are in the default walking order that they can't, and will cut down on filler expository)
Sudden Ambush: Darkspawn sweep up from the side, or bandits attack the party from behind. We know who is closest, and players can strategize accordingly.
Also, this can help establish "moving buddies" (yay, Toy Story, ftw), and establish some travel camaraderie. Remember, characters can break the formation, and this won't hinder gameplay in anyway, but I think will help establish some sense of order. (Fifteen people is a lot, yo)
Because I'm pictorially obsessed, should you guys like the idea, I will have a completed version with photos for the Group Resources. Any suggestions where your character should go to the order? Vehemently opposed to the idea? Don't really care where you stand? Reply anyway. I don't want to step on toes.