As we're on the topic of a promo video as well as an RP video, i keep having images of the MW2 intro(s) and how we can make it sorta like that.
Maybe instead of inter-unit communications, we keep it to the perspective of one side and throw some original MW2 music to it (or something equally as awesome). You'll notice that in most of the mechwarrior intros (even the MW5 series restart vid) the other(silent) side wins and makes the struggle look awesome. Since this game is MP, we could do one promo for each side.
We draw up scripts and do some sound editing after recording, giving the voices the right 'feel' (or simply use rad hanzo's solution).
We'd have to have multiple people using fraps, including some static cameras, and there would definitely be more than one take.