Scott, I took your UCLA "Protag's Arc" workshop this fall and loved it. Not in a million years would I ever think to apply your Disunity/Unity arc to Wizard of Oz but it actually seems like a great case study, so thanks for throwing that tidbit into this post.
What about films with a psychological bent, like A Beautiful Mind where the mental illness is the antagonist, or this year's Moon? Is Moon along the same lines as Castaway?

Another great example of a protag in disunity is 12 Monkeys, where Cole's antagonists take several different forms, almost all are institutions: the repressive, underground society of the future (his present), the mental institution in 1990, law enforcement in 1996.

But also several characters briefly assume the role of antagonist who hinder Cole's attempts at unity: Brad Pitt's Jeffrey Goines and even Madeleine Stowe's Dr. Railly.