This.
I hated the fact that I was railroaded into project purity. It was so stupid. Why couldn't Fawkes do it?
Also, it was so black and white. Either you go in, and are a hero, or don't go in, and are a demon.
Fawkes couldn't do it because Bethesda made the mistake of listening to the people on the forums.
Really.
Originally the "Lone Wanderer" was supposed to be the "Lone Wanderer", and not have companions/henchmen/hirelings/whatever you want to call them. Then people started asking for companions. With great frequency. Like constantly. They wanted to be able to have companions. So Bethesda gave in and came up with the companions. But it wasn't until later in the development, and some aspects of the companion thing might not have details worked out as well as they could have hoped. Like realizing that the "Lone Wanderer" could possibly have a supermutant who was basically immune to radiation, a ghoul who was healed by radiation, or a robot that wasn't bothered by radiation, with them at the end. Think about the story; makes a lot more sense if the choice at the end is just Sarah, and you. Might not be a better story, but it makes a lot more sense why your "not effected by radiation" companion can't go in and push three buttons for you.
Josh posted about the dlc; they are not planning on doing a "Broken Steel" to let people play after the end.
The quote from Josh Sawyer:
What was the decision behind the definitive ending? There was a lot of moaning and arguing about Fallout 3 having a hard ending and in the end we got a DLC that allowed for an open ending. Don't you expect the same to happen?
Sure, but I also think that would happen if we allowed players to play past the end of the game but didn't show the impact of their actions on the world. There is a lot of reactivity to your actions at the end of the game and we give the player a very clear warning when they are approaching the main plot's conclusion. We felt that having an endgame denouement with a large number of far-reaching effects was too important to either allow the player to continue playing in a world that didn't react to any of those things or make the endgame states minimalistic. There is a lot of reactivity to your actions at the end of the game and we give the player a very clear warning when they are approaching the main plot's conclusion.
Any dlc will be set before the end of the game, like the dlc for FO3 before Bethesda gave in again and ruined the end of the story that I liked.