Okay I know my next suggestion won't be on the top of everyone's priority list but I would like to see more weather effects in the game.
For example, torrential rain, thunderstorms, gales, blizzards, fog (etc) and how these weather conditions could affect battling enemies. One little aspect I liked in ME2 was how Haestrom's sun affected Shepard's barriers so it would be interesting to see how a new protagonist would deal with certain other weather conditions. This would be something different because the majority of the trilogy was set in a calm static environment (especially 2 and 3). The only two instances where I can vividly recall there was a different weather pattern was Noveria (with the snow) and Pragia (for the brief appearance of rain).
I know this isn't something major but it would be nice to see
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(I'm expecting some wiseass to say go outside or play Mass Effect 3 with the "Rainy Mood" in the background
)