Tirian Thorn wrote...
If all the Reapers were at Earth, then it would be a good way to wipe out the allied forces.
With the collector base gone, the reapers may not have another way to make reapers. The Citadel has probably always been used for collecting bodies to make other reapers.
Based on earlier evidence it is believed that the reapers only believed humans to be useful for reaper form.
Now, that isn't to say that the other races won't be harvested or used in some way - maybe made into destroyers but it seems that the big ships are only created uses the best of stock. In this cycle - humans.
Sorry for the late answer.
True again. The Reapers are dispatched through the galaxy and there is alot of them. But the bulk of their forces (or at least the "elite force") is on Earth with Harbinger himself to lead them. They know we have the Crucible and they know we're coming for the Citadel in an all-out battle and they're waiting for us, well prepared. Could it be that they've underestimated the power of the allied forces ? I don't think so...
As for the Citadel being used to collect the humans and eventually process them, why not (though they could have waited till they exterminate the fleets and then move it to Earth) ? It's also killing two birds with one stone : a new "collector base" and a trap to lure the allied forces on their own destruction.
I might be completely wrong and I'm getting totally out of topic, but I'm very interested in this part of the story (besides the IT) and I find the "Crucible" (as giant super weapon) and moving the Citadel to Earth, too simple and too convenient. A clear answer about "Why London ?" would be also cool

...