There was one piece of concept art for Andromeda that looked sort of the Presidium, but not quite. There was some speculation on whether it might be the inside of the Ark, and whether the Ark might be the Citadel's replacement.
It would be nice if the Ark was a major hub since it could provide oppertunities like quests to help forge a connection with the player and make them care about the Ark and it's people for other reasons than because the game thinks you should.
One of the problems I had with Earth was that the game seemed to assume that I personally cared about Earth but the thing was that while my player character likely would to an extent, me as the player did not since I had no connection to the place: The ME3 prologue was about the most I'd seen of Earth and during the aforementioned prologue, the most I talked to anybody there for was about a minute or two.
Basically, the label of "Earth" could have been slapped over the label of "Illium" and it'd been the same result in terms of me personally caring.
That's not to say it would have made a difference if they'd shown Big Ben being broken and burned by a Reaper since that's not a national icon that belongs to my country and even if it was, I've likely been so desensitized by films that it would not have had much of an impact. Admittedly, there's not much the Reapers could do to the Little Mermaid statue that had not already been done. The poor thing.