In the comics, Hank Pym created Ultron and Ultron in turn created the Vision, essentially making Pym the Visions grandfather. There is a theory on a Pym/Ultron connection (more on that in a minute), but maybe Pyms expertise comes into play when creating the Vision. The Vision in the comics was built from the remains of Jim Hammonds synthetic body (it gets a bit more complex than that, but thats the gist of it). If that holds true in the movies, Stark and Banner may need some additional assistance in creating The Vision to combat Ultron. And if the previous theory of Hammond being active at some point in the past, perhaps working alongside with Pyms Ant-Man, proves to be correct, who would know how Hammond works better than Pym? If Pym plays some role, even if its just his technology or previous research he did that Tony and Bruce use, that would help to tie Ant-Man even more firmly to the MCU, while also serving as a nice little nod to Pyms connection to Vision in the comics. For most viewers, they may not even get the significance. But for longtime Avengers fans, it could serve as a great Easter egg.
Percival Constantine is the author of several novels and short stories, including the Vanguard superhero series, and regularly writes and comments on movies, comics, and other pop culture. More information can be found at his website, PercivalConstantine.com