I think a possible workaround for PS3 players to get to make the major choices in the first game could be done simply by altering the dialogue that you have with Miranda during the shuttle flight before meeting the Illusive Man for the first time.
More specifically, the questions that she asks you during the conversation could allow PS3 players to choose who they saved, who they let die, and so on, so that PS3 players still get to make the major decisions in the first game, without having to play it.
And honestly, playing the first game isn't really as necessary as people are making it out to be. I personally only have one character imported from the first game, while the majority of my other characters I have in ME 2 were started from scratch (since I don't like going back to the first game because I just can't stand the first game's dull combat).
