In this way, the first one to side with Captain America during the Civil War is Ant-Man. As this year's solo movie has revealed, there is a big gap between the conceptions of Hank Pym and Tony Stark's conceptions. So we can only assume the Scott Lang (a pupil of Hank Pym) will see the threat posed by the need for safety.
And this is the reason why Hank didn't want the Ant-Man suit to be exploited as a weapon: it can bring great benefits (just like the Registration Act), but it can bring even greater destruction.
Furthermore, Hank was already known to have a pretty interesting idea concerning superheroes, in the sense that he doesn't consider them worthy of being called this way. So why this conception wouldn't become the one of his pupil?
And there is also that end-credits scene, in which he is basically called the alternative to Iron Man…
On the next page, Hawkeye