I have mixed feelings about this trailer. We know what it tells us, but we know nothing about how much it tells us about the actual game.
Maybe we won't see anything of London or SniperBen in the game, maybe they are an integral part of the storyline. Maybe the scene takes place at the beginning of the game, or maybe all this happens close to the end of the story.
It is fun to speculate though.
What bothers me a bit is, if this is the situation at the beginning of the game, then rallying allies after that will take a lot of time, which makes earth a reaper occupied place for weeks or even months. That will put you as player under the feeling of time pressure right from the beginning of the game. I don't know if i like that idea, because it might give you the impression you have to rush through the game and persue the main storyline as quick as possible to end earth's suffering.
And then the writers should come up with a real good explanation of how the reapers got there so fast in the first place. They depended on a mass relay to get to the galaxy for millions of years. What changed that? Did they hail a taxi?
Wouldn't want to be in the writers shoes anyway. So much to consider, so many variables. Gives me a headache thinking about that. Telling such a story isn't so hard but at the same time giving the players the impression their past choices matter is. Good luck with that. But i'm sure they won't dissapoint us.
Can't wait to see more news about the game.