Secret Invasion

Now here is a storyline that could be adapted for the MCU starting right from next year "“ what if Iron Man isn't Iron Man himself, but just a clone or, say, a shape-shifting alien? What if, over the course of, say, an entire MCU Phase, all the heroes are replaced in the same way by some aliens who possess this ability?

Of course, this might be a bit tricky, since the Skrulls are now owned by 20^th Century Fox. But would you have believed a couple of years ago that Spider-Man will join the MCU? So let the Secret Invasion begin already!