Re: The Design & Origin of ULTRON
I think it is possible that Robert Redford's SHIELD character may have commissioned Pym to work on the Ultron project in secrecy, with the goal to replace Avengers in the future with an army of Ultron. However, after Pym finished with its AI, they couldn't build an ideal android body for it so he turned to Stark for help. Stark is now no longer Iron Man so he decided to help, but Pym's AI becomes sentinel and gone rogue. Stark felt responsible so he becomes Iron Man again so he can put down the monster he helped created. In the Ant Man movie, it could deal with the aftermath of A2.
Steve Rogers: "You're my friend"
Winter Soldier: "You're my mission"
Steve Rogers: "Then finish it, because I'm with you 'til the end of the line"