The deck is still stacked against ME. They have the Humans, Asari, Turians, Salarians, Krogan, Batarians, Volus, Elchor, Drell, and the Vorcha. They came together explicitly because of the danger posed by the Reapers. Trouble is, you're not going to be able to convince them that the SW universe is on the same level as the Reaper threat. The Asari are going to want to talk, the Salarians and Turians would want to investigate and study, the Volus and Elchor would prefer to trade. About the only two groups that would be gunning for a fight would be the Krogan and Vorcha.
The second you try and elevate the situation from a straight-up fight and muddle it with things like "motivation" and "reason", you see how quickly the whole thing falls apart. It has to be looked at as a straight, head-on fight or nothing at all. You have to hit the ground with no assumptions or you have to spend pages identifying crucial factors and outlying the premise in a complete study.