I have been reading some early Hank Pym adventures (albeit as Giant Man moreso than Ant-Man) and part of me would really like a retro, Two-Fisted Man Of Science and His Girl Friday kind of story like the Tales To Astonish stories have been. I wouldn't want Hank Pym to be portrayed as a wife beating nutcase, nor as the guy who is not quite as smart as Tony Stark and not quite as strong as Thor (which in and of itself I thought was a very good retcon but only because it addressed his pettiness and jealousy which other writers emphasised).
As I said, if Edgar Wright is still developing the film, then Eric O'Grady makes sense. What is less clear to me though is how you would incorporate the Irredeemable Ant-Man into the Avengers (assumingly) for the sequel. He does not play well with others and giving him a conscience I think would defeat the point.
Scott Lang I think actually can work for a film. He's a single Dad with a cute little daughter, just a work a day engineer who happens to be really smart. Hollywood loves cute kids, and you can introduce a love interest for him and do cutsey things with her and the kid. And it would also make him demonstrably different from the other Avengers -- Scott Lang is the "everyman," not a living legend or international celebrity or demigod. And unlike the hyper-professional Black Widow and Hawkeye, he brings a real "man on the street" point of view.
Another question is who the badguy would be? I can only think of a handful of Ant-Man villains -- Whirlwind/Human Top, Egghead,uh... Porcupine? -- and they are not exactly world beaters. Egghead seems like the natural choice if you use Pym (maybe Whirlwind can be his henchman?), but the others are less clear.
My main thought is that whomever they use, hopefully it will have the same effect it had for Shellhead and re-establish Ant-Man as more of a major player in the Marvel Universe. Just my thoughts.