Okay, lets imagine some crazy but still feasible story lines you would like to see but know that would never see. Mine is based on canonising one of the ME3 endings and "ramping it up" to top a galactic genocide.
Shepard took the "control" option at the end of ME3 and is now in control of the Reapers and spent several years peace keeping and rebuilding, however there are some complications.
The Rachni are back and they still hate the Reapers for what they did, they start spawning new hives and indulge in some genetic modification to spawn newer and deadlier forms including giant biological warships like the Leviathan. To draw the Reapers into conflict they start attacking the other species, Machine God Shepard responds.
The new Rachni war rapidly escalates and spreads across hundreds of star systems and the other races fight back, unfortunately machine God Shepard has completely lost touch with his/her humanity and adopts a purely pragmatic and logical approach and thinks nothing of bombarding planets, using the other races as tactical bait/meat shields if it thinks that its better "in the long run" so they are also forced turn on Shepard and the Reapers.
All the other races are now stuck in between a swarm of billions of Rachni who are now determined to wipe everything out and the Reapershep who brutally puts down any resistance from anyone, the Council and the Alliance form a task force to try and stop the madness.
Many of Shepards former crewmates are enrolled as they knew Shepard and fought the Rachni, they are faced with stopping or destroying their former commander and finding a way to stop the Rachni.
The end would be three giant RGB explosions.
Shepard took the "control" option at the end of ME3 and is now in control of the Reapers and spent several years peace keeping and rebuilding, however there are some complications.
The Rachni are back and they still hate the Reapers for what they did, they start spawning new hives and indulge in some genetic modification to spawn newer and deadlier forms including giant biological warships like the Leviathan. To draw the Reapers into conflict they start attacking the other species, Machine God Shepard responds.
The new Rachni war rapidly escalates and spreads across hundreds of star systems and the other races fight back, unfortunately machine God Shepard has completely lost touch with his/her humanity and adopts a purely pragmatic and logical approach and thinks nothing of bombarding planets, using the other races as tactical bait/meat shields if it thinks that its better "in the long run" so they are also forced turn on Shepard and the Reapers.
All the other races are now stuck in between a swarm of billions of Rachni who are now determined to wipe everything out and the Reapershep who brutally puts down any resistance from anyone, the Council and the Alliance form a task force to try and stop the madness.
Many of Shepards former crewmates are enrolled as they knew Shepard and fought the Rachni, they are faced with stopping or destroying their former commander and finding a way to stop the Rachni.
The end would be three giant RGB explosions.