I always thought Moriarty had a point about Billy Creel, There's something creepy about his relationship with his "daughter" Maggie, I agree that he just might have killed her parents himself.
Always thought it might have been a good quest if you had to go and find the truth about Maggie's parents deaths.
could have been entitled "Little orphan Maggie"

Any other ideas about possible quests?

Freeing Gob and escorting him to Underworld would have been nice.
Or having Gob wait for you outside of Megaton before escorting him to Underworld and then informing Moriarity about Gob's escape attempt. :bolt:

I want to go to the Commonwealth, and see what became of MIT.

I always thought Billy was OK. Since Colin Moriarty is a selfish, greedy piece of scum, he cannot comprehend altruism or human kindness. It's only natural that he would suspect Billy's motives. And Maggie seems pretty well looked-after, as kids in the wasteland go.

I like the idea of liberating Gob, though. The first part of the quest could be to find incriminating evidence against Colin, so he would let Gob go. Maybe Colin screwed Jericho at one point, and you can threaten to tell Jericho if he doesn't let Gob go.

Billy Creel's creepy?? Moriarty has an Andale Shack key.

a quest to go to the commonwealth. i would like to see that story because its only accessible via capital wasteland. and also a bit of history too.