OK, mine wish list for MP
1) "Omnigel converter" (similar to ME1) to be able to convert crap or good ammo or equipment into something useful (at some loss of cause). I would happily trade 5 boxes of explosive or cryo or disruptor ammo into one box of AP ammo, or 5 sniper rife amplifiers into one shotgun amplifier.
2) Appearance customization - It would be cool to be able seeing all the shining ribbons and insignia on the character. Like so and so number of golden headshot medals will give you golden headshot insignia. However, insignia, earned on bronze difficulty will not show on higher difficulties.
3) I fully support some possibility of customization for abilities, with limitations of cause. Say, you can change just single power, from the limited pool, available for the class (and maybe race). Make it ultra rare card. Add "weight" factor - like you have just certain power capacity, so than sometimes you have to trade two "light" powers for one "heavy" - there are the ways to make it work. Alternatively, place more thought into character development, because now some characters are no fun (at least for me). Now, when I think about it, I would change just Justicar - to be able casting BE at a distance on all units, and not just a lifted ones (like replace Pull with Throw or Singularity or make Pull priming all targets).
Also Asari Vanguard - for her Stasis just make no sense, and therefore she is 6-0-6-6-6 always for me. However, if we could replace Stasis with Warp for her, that would be entirely different story, making 6-6-6-4-4 very interesting.
4) Blood textures on the walls and uniforms of CQC characters would be cool as well.