The thing is... they don't need to create a dramatically different story to include other options. I haven't played thieves guild yet (because my main isn't a thief) but I imagine having a character approach you in the beginning and asking you to be the Iron Wheel's "inside man" wouldn't have been too hard. Maybe they do that... but I am assume they don't.
I voted yes (knee jerk reaction) but think it would be better if the Morag Tong had their own DLC down the line.
The DB story could have the player, at the moment of assassination, choose to let the victim live with the ultimate overarching story leading to the same resolution.
It's not like we're asking for ZOS to do anything revolutionary in terms of narrative or story design.
Morag Tong forever. I really hope they implement it into the game although i agree it is highly doubtful that it would come into the game next dlc. I assume it will either be added as a new dlc or not at all.