Well actually, one of my first thought in AoA was "why are they bringing that many warships? ... Well, the guys on the other side are humans, maybe it's some horrible dictatorship, and that its what this mod is about, fighting for the "Blue Planet"?"
Two missions later "the Shivans destroyed Earth anyway ? I was wrong, but that's even more awesome !"
Later "On the other hand, I would feel bad if it happened canonically; if the last mission for fs1 was for nothing."
Last mission "or was I(wrong)?"
Which actually is brilliant story-telling, because players always wonder who they will fighting in the mod the campaign they're playing. In a "return to Sol" scenario, in my mind, it was either evil humies/many factions of humie at war, good reunion followed by shivans/other aliens, or shivans/other aliens already there.
By the end of the campaign, I had forgotten about my early therories (well, up until the line "do you come in peace?" popped up and wasn't instantly answered to), and then: boom! Surprise!
Its like saying "Sorry guys, Mr McAwesome couldn't come today, but I brought Cool Joe instead" and later "Hey you know what? Mc Awesome came anyway!"