Originally Posted by InJustice
Except you do it at the cost of Hank Pym's character. You effectively strip away his depth, and guilt when he's responsible for Ultron (certain continuities showcase him being responsible for building it, others take it one step further by showing how Ultron is the personification of Hank Pym's darkness). That is honestly more interesting to watch than another "experiment gone rogue."
Though I must say, after rewatching Avengers, it seems like Ultron was heavily foreshadowed as a method for dealing with huge scale events like the Chitauris coming to Earth (repeated dialogue featuring Phase 2, and how Phase 2 was designed to stop events like Chitauris).
Iron Man 3 foreshadows it even worse.
That said, what you've described from Pym is definitely another "experiment gone wrong" and all of it works just as well with Stark. Now, what you don't get is Pym. Widow and Hawkeye were founding Avengers at his expense. Lang will be focused on at his expense. Ultron will be made by the Avengers at his expense. That's rough for Pym fans. That said, Pym was never on the table. He was never an available option. And the quality of the story doesn't actually go down...