Comic Book Movie brings us the following:
Now, according to one of The Daily SuperHero's screenwriting sources—who is closely plugged into Marvel movie development ideas—word on the street says the Hulk sequel might be getting a treatment based on some of the Bruce Banner-specific concepts in Marvel NOW's Indestructible Hulk comic.
In case you are not familiar with the Indestructible Hulk comic, the basic premise of the story is that Hulk is an agent of S.H.I.E.L.D. To get into more detail about the current comic title, Banner feels he needs to give back to society so he approaches S.H.I.E.L.D. and asks for a lab where he can give the world inventions that will help society in exchange for letting S.H.I.E.L.D. "point and aim" the Hulk whenever needed.
So why would this work on the big screen? First of all, Marvel Studios president Kevin Feige has openly said the key to another Hulk film is Ruffalo's portrayal of Banner. Hulk is just the icing on the cake in any future movie. Plus, Marvel's continued vision and focus since the days of Stan Lee running the show has been all about the person and his or her character behind the hero. So far this has been true in Marvel's Phase 1 and seems to be continuing during Phase 2 as well.
In the case of an Indestructible Hulk-based movie script, Banner would definitely be a big focus. As would S.H.I.E.L.D and having Hulk as a SHIELD agent brings a more realistic use for the green hero instead of telling the story that he's always running and hiding to stay away from stress, anger and putting people in danger.