No this will not involve any of the actual story. Yes this is the same universe as the games. No it will not include Mass Effect 3 lore or story.

You are still limited to one class just like the game, and the weapon restrictions that come along with that class.

Yes crossovers are allowed but for once I am going to put a limit on what can actually be used. For example: Destiny, Halo, and Borderlands are all acceptable for a crossover. Mha is not acceptable.

Scenario 1 (Mass Effect 1 pre Sovereign): You arrive on the citadel, the central up of the Alliance and the home of the Council. As you look around you can see a few unique looking individuals. As well as that you see a crowd gathering around something while C-sec officers force their way through the crowd of people.

Scenario 2 (Mass effect 1 post Sovereign): The news spread throughout Council space, a large ship had attack the Citadel while leading an army of Geth. While the Alliance won many were lost in the fight and efforts were underway to rebuild. The council has sent out requests for multiple jobs all needed to aid in the rebuilding.

Scenario 3 (Mass effect 2): Omega the most dangerous and crime filled place in all of Alliance space....or as you called it home. You heard news about an outbrake happening in the lower levels but what could you do about that?

Scenario 4: Make Your Own.