Re: Could Ultron be...?
There's been plenty of suggestions to this effect; but what makes Ultron's story unique to Hank Pym is the whole oedipus complex that develops between Mommy (Janet Van Dyne), Daddy (Hank Pym), and Son (Ultron). It's a twisted Freudian freakshow, but it's really what's driven Ultron all along over the decades.
If you throw away Ultron's connection to Hank Pym, you turn him into just another Killer Robot. If you keep the Pym connection, then there's a really chilling psychodrama going on there between Creator and Created, with Pym as the "failed" hero who never can seem to live up to the high standards of his all-star comrades, Ultron as his greatest (and simultaneously worst) creation, and Janet as the object of *both* their (often unwanted) affections.
Ultron just doesn't work on a psychological level with anybody but Pym. Pym has to be his creator, and Janet has to be his oedipus complex. That's what separates his story from the usual Killer Robot stereotype.
THE COTTON AVENGERS
...They move like slick cotton on oil.