What do you think ME4 is about?

Reaper War is over. Destory ending is canon. Shepard is alive. New Council (Krogan and Quarians included) starts the rebuilding of the world. Shepard is happy to be alive and well, helps with some minor issues but then the new threat appears. Yaghs starting to attack random worlds. They are way too organized and well-armed to think it's their own doing. They have contacts on the Citadel. Shepard is sent to investigate. First and obvious suspects are Salarians. We know they tried to uplift Yaghs and we know they made the same mistake before. Hence, STG is trying to solve yet another possible leak and Kirrahe joins the team. In fighting and detective investigations we finally uncover the truth. It was Asari radicals all along. They were worried about the loss of power and authority in the new Council, they were worried about the barbarians and other 'minor' races gaining too much power, they also had personal grudge against Shepard himself (the major culprit is the Asari councillor?).

Something like that

/r/masseffect Thread