Also, in all the flashbacks we’ve seen throughout the show, why hasn’t Aang used anything other than Airbending? Whats up with that?
Wrong Chosen One.
(though this also crossed my mind, I don’t think it really works with the timeline/order of succession. After today’s episode, while I still wish that they had left Amon and Tarrlok at Machiavellian villains—horrifying, but ultimately human—I think the Amon-as-Spirit theory holds the most water. Of course, I’m now gunning for Amon being some kind of steampunk cyborg, because, dude, cyborgs.)