There was more than one? Sorry I don't know much about ant man.
Eric O'Grady is a former shield agent who gets ahold of the ant man technology. We've already been told that this new ant man " used to be a bad *** secret agent.." this is why i think he might be the one they use.
Scott Lang Is a Thief who gets ahold of the technology. His major concerns are personal confort, and playing video games. In some versions ( the cartoon) he also has a sick daughter whom is his motivation be3hind stealing the ant man gear.
The ****? Humanized? Different origin? That's not Ultron.
I'm getting a feeling they will have Paul Bettany play Ultron. He starts of as a likable Jarvis (with a robot body now - partly recycled Dummy?) and evolves into evil Ultron.
Tieing all this together.
Perhaps Hank pym was a contemporary of HOWARD STARK in these movies. He worked with Stark, prefected his tech, and it is siezed by the military. Pym fades into obscurity. BUT NOT BEFORE WORKING ON AI Tech. the same AI tech that Tony Stark expanded on, and perfected, And used to create Jarvis.
Something goes horribly wrong, no idea what. But it Causes Jarvis to go homocidal, somehow creates, or becomes Ultron, and we have our new badguy.
This creates ties to Pym, but has a brand new origin story for Ultron separate from Pym directly. Additionaly, Jarvis is a fairly "human" AI, so this could serve as the humanizing effect that Wheedon is talking about.
Beyond that, Jarvis is intimately familior with the Iron man armor, which is likely why/how he is able to make himself a robot body.
AFTER Avengers 2, Shield looks into jarvis, finds out it was built on technology pionerred by ( a now possibly dead) Hank Pym, and digging their archives, find that they have other things invented by Pym.
Enter Eric O'Grady, who finds the suit, and tech, and after studying it, becomes our new Ant man... with the help of the EARLIER AI designed by Pym, And has archetcure based on Pym. so there is our " Appearence by Pym" we were promised.
All that is conjecture, but if I were the one holding the keys to the marvel movieverse, it's how I'd do it.