The movie should've never been made in the first place.
The whole issue here is that Wright was taking an ensemble cast member(s) and isolating them into a standalone movie with no connective tissue to the team they've canonically been attached to for the past 50 years. That kind of nonsense would have flown in 2006 when standalone CBMs were the norm; but after 2008, the interconnected MCU --- anchored firmly by The Avengers flagship, the raison-d'etre for the existence of Marvel Studios in the first place --- took precedence, and Wright stubbornly refused to play ball with "the bigger picture" until the bitter end.
The simple fact of the matter is that Hank and Janet (and even Scott Lang) never required a separate movie to introduce them into their canonical home in The Avengers, any more than Wanda or Pietro did. Now, Marvel is stuck with this anomaly of a film that they're trying to fit back into place within an Avengers canon that's already been shredded by Wright's epic procrastination.
I see three options, none of them even remotely viable:
a) give Wright his movie back, and let him make his standalone piece.
Fanboys will revolt at the wholesale assassination of comic-book canon, but maybe the movie will find a cult audience for yet another quirky but fun Edgar Wright genre parody.
b) give it to a journeyman director/scab, and try to justify Old Ant-Man and his Padawan Protege requiring a $150-mil budget for a superhero that no general audience member has heard of or cares about. (Chants of "John Carter, John Carter" begin, ominously, in the distance.) Then, when the movie tanks in epic fashion, try to justify shoving those same superheroes that nobody wanted to watch into The Avengers proper.
Again: fanboys revolt.
c) Scrap the Ant-Man film altogether, and quietly introduce the core characters (Hank and Janet for sure, Scott maybe) into Avengers 3, and make them quirky and interesting enough to gain new fanbases (i.e., use the same strategy they're using on Scarlet Witch and Quicksilver in Avengers 2).
It's a crapshoot. Hit or miss. But it's not a $150 million gamble, and is a much safer bet within the most profitable franchise in movie history.
d) Just scrap the film altogether, and the characters along with it. Quietly accept your losses, learn your lessons, move on. An Avengers without Hank and Janet isn't the end of the world. Let fanboys weep for what might have been.
Imho, C is the best option, and the least costly gamble for the studio, and the one most likely to make fanboys happy since it's a helluva lot closer to a canonical approach than anything that had been reported in Wright's INO version of the Ant-M(e)n story.
So....C is the *least* likely option that the studio will take. Seems inevitable now that they're going with option B.
Say hello to the ghost of John Carter, Disney. Haven't we trod this ground already...?