Something i thought off In Mass Effect 3, alot is going on. Like it or not, you can't deny all that happens (Batarians nearly being wiped out, Attack on Palaven etc etc) So why not make a game mode where you play maybe a smaller campaign...but not as Shepard. You create your own character who have his/its moments. Say for example you want to play as a Turian, then you start off with the Invasion of Palaven and have to fight and evacuate. Or you might want to play as a Batarian and you are a soldier on a ship that manages to escape (which would also give us a better understanding of the Batarian society) Or, if you like me love big guns...You play an Elcor, holding off Husks with a chaingun on your back and tackling a Brute head on as you defend civilians on Dekuuna. All of these things culminating in the battle of Earth, ending with (here's a minor twist)... The ending your Shepard chose! Yes, you import your Shep from ME3 and fight through things, maybe seeing him on pictures or vidscreens and so, and then your game culminates in a blue, red or green explosion (or just your death)
Love it, hate it, want it, deny its existance. This is my idea.