That would involve you doing practically every side mission, but my understanding it is possible.
You are right in not trusting EA, given their track record, but in this one specific case, I feel they are doing it right. The Microtransactions serve as accelerators, and so are unnecessary, and the Multiplayer serves singleplayer rather than vice versa.
Maybe there is enough of the old Bioware core to keep the EA evil at bay. Who knows.
I was under the impression that you needed to participate in the multiplayer to get your battle readiness points high enough for the best ending. If that isn't necessary, then I have no problem with the sort of multiplayer that ME3 offers.
Still, I'm a pessimist, and I have little doubt that even such innocuous multiplayer can turn evil, as more and more time and money is spent on developing it rather than the single player. Not to mention a more subtle concern. Multiplayer typically involves shooting at each other, or other forms of combat. It doesn't involve rpg elements very much, so as multiplayer grows in importance, it will skew the main game toward combat and away from rpg elements as well.
As far as I'm concerned, you simply can't beat Witcher 2: Enhanced Edition, which offered an arena mode where you face increasingly difficult waves of enemies. This was combat galore, but in between fights you got to shop, pick prizes, and level up your character, so you had all of the rpg elements involved as well. And there were even some online elements in the form of being able to post your score online and seeing how you rank compared to other players. Something like that wouldn't prejudice the game one way or another and offers elements for everyone. Multiplayer like in ME3 is only for the people that like shooters and action-oriented gameplay. And though they can simply skip it and ignore it for now, it will invariably affect the way future games are developed, making it too important to simply ignore.
